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 $86.28   10.379%   $95.235   $95.24   $95.25   $95.20  
  Purchase #2 $125.25   4.102%   $130.3878   $130.39   $130.40   $130.40  
  Purchase #3 $49.80   5.198%   $52.3886   $52.39   $52.40   $52.40  
  Purchase #4 $124.57   3.571%   $129.0184   $129.02   $129.00   $129.00  
  Purchase #5 $67.92   3.489%   $70.2897   $70.29   $70.30   $70.30  
  Purchase #6 $61.46   13.521%   $69.77   $69.77   $69.75   $69.80  
  Purchase #7 $64.41   3.827%   $66.875   $66.88   $66.90   $66.90  
  7 purchase totals = $579.69       $613.9645   $613.98   $614.00   $614.00