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 $37.54   10.719%   $41.5639   $41.56   $41.55   $41.60  
  Purchase #2 $214.57   12.760%   $241.9491   $241.95   $241.95   $241.90  
  Purchase #3 $94.80   9.722%   $104.0165   $104.02   $104.00   $104.00  
  Purchase #4 $236.76   12.201%   $265.6471   $265.65   $265.65   $265.60  
  Purchase #5 $180.89   11.571%   $201.8208   $201.82   $201.80   $201.80  
  Purchase #6 $87.73   3.269%   $90.5979   $90.60   $90.60   $90.60  
  Purchase #7 $16.25   4.313%   $16.9509   $16.95   $16.95   $17.00  
  7 purchase totals = $868.54       $962.5462   $962.55   $962.50   $962.50