Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $167.47   9.585%   $183.522   $183.52   $183.50   $183.50  
  Purchase #2 $244.33   6.328%   $259.7912   $259.79   $259.80   $259.80  
  Purchase #3 $182.55   10.268%   $201.2942   $201.29   $201.30   $201.30  
  Purchase #4 $218.63   8.147%   $236.4418   $236.44   $236.45   $236.40  
  Purchase #5 $221.59   8.561%   $240.5603   $240.56   $240.55   $240.60  
  Purchase #6 $107.34   3.160%   $110.7319   $110.73   $110.75   $110.70  
  Purchase #7 $211.52   10.604%   $233.9496   $233.95   $233.95   $233.90  
  7 purchase totals = $1,353.43       $1,466.2910   $1,466.28   $1,466.30   $1,466.20