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 $116.65   6.261%   $123.9535   $123.95   $123.95   $124.00  
  Purchase #2 $224.50   4.541%   $234.6945   $234.69   $234.70   $234.70  
  Purchase #3 $209.33   10.725%   $231.7806   $231.78   $231.80   $231.80  
  Purchase #4 $29.29   11.366%   $32.6191   $32.62   $32.60   $32.60  
  Purchase #5 $42.88   10.659%   $47.4506   $47.45   $47.45   $47.50  
  Purchase #6 $163.35   12.635%   $183.9893   $183.99   $184.00   $184.00  
  Purchase #7 $233.54   3.132%   $240.8545   $240.85   $240.85   $240.90  
  7 purchase totals = $1,019.54       $1,095.3421   $1,095.33   $1,095.35   $1,095.50