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 $155.27   11.821%   $173.6245   $173.62   $173.60   $173.60  
  Purchase #2 $115.62   3.173%   $119.2886   $119.29   $119.30   $119.30  
  Purchase #3 $177.98   5.622%   $187.986   $187.99   $188.00   $188.00  
  Purchase #4 $59.95   4.491%   $62.6424   $62.64   $62.65   $62.60  
  Purchase #5 $58.43   10.109%   $64.3367   $64.34   $64.35   $64.30  
  Purchase #6 $119.41   6.674%   $127.3794   $127.38   $127.40   $127.40  
  Purchase #7 $15.63   10.696%   $17.3018   $17.30   $17.30   $17.30  
  7 purchase totals = $702.29       $752.5594   $752.56   $752.60   $752.50