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 $164.62   5.720%   $174.0363   $174.04   $174.05   $174.00  
  Purchase #2 $110.35   13.532%   $125.2826   $125.28   $125.30   $125.30  
  Purchase #3 $160.62   11.552%   $179.1748   $179.17   $179.15   $179.20  
  Purchase #4 $108.66   4.212%   $113.2368   $113.24   $113.25   $113.20  
  Purchase #5 $156.44   6.816%   $167.103   $167.10   $167.10   $167.10  
  Purchase #6 $56.91   4.837%   $59.6627   $59.66   $59.65   $59.70  
  Purchase #7 $223.50   10.318%   $246.5607   $246.56   $246.55   $246.60  
  7 purchase totals = $981.10       $1,065.0569   $1,065.05   $1,065.05   $1,065.10