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 $189.87   6.367%   $201.959   $201.96   $201.95   $202.00  
  Purchase #2 $90.95   6.643%   $96.9918   $96.99   $97.00   $97.00  
  Purchase #3 $32.27   7.296%   $34.6244   $34.62   $34.60   $34.60  
  Purchase #4 $75.77   3.290%   $78.2628   $78.26   $78.25   $78.30  
  Purchase #5 $31.68   13.438%   $35.9372   $35.94   $35.95   $35.90  
  Purchase #6 $51.64   4.482%   $53.9545   $53.95   $53.95   $54.00  
  Purchase #7 $244.74   6.274%   $260.095   $260.10   $260.10   $260.10  
  7 purchase totals = $716.92       $761.8247   $761.82   $761.80   $761.90