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 $72.76   3.226%   $75.1072   $75.11   $75.10   $75.10  
  Purchase #2 $217.87   12.696%   $245.5308   $245.53   $245.55   $245.50  
  Purchase #3 $47.48   11.730%   $53.0494   $53.05   $53.05   $53.00  
  Purchase #4 $44.66   3.315%   $46.1405   $46.14   $46.15   $46.10  
  Purchase #5 $168.32   8.433%   $182.5144   $182.51   $182.50   $182.50  
  Purchase #6 $240.48   10.598%   $265.9661   $265.97   $265.95   $266.00  
  Purchase #7 $216.88   8.822%   $236.0132   $236.01   $236.00   $236.00  
  7 purchase totals = $1,008.45       $1,104.3216   $1,104.32   $1,104.30   $1,104.20