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 $84.48   12.441%   $94.9902   $94.99   $95.00   $95.00  
  Purchase #2 $161.57   4.385%   $168.6548   $168.65   $168.65   $168.70  
  Purchase #3 $55.54   13.635%   $63.1129   $63.11   $63.10   $63.10  
  Purchase #4 $19.38   7.238%   $20.7827   $20.78   $20.80   $20.80  
  Purchase #5 $95.61   13.556%   $108.5709   $108.57   $108.55   $108.60  
  Purchase #6 $195.43   10.618%   $216.1808   $216.18   $216.20   $216.20  
  Purchase #7 $21.98   5.316%   $23.1485   $23.15   $23.15   $23.10  
  7 purchase totals = $633.99       $695.4408   $695.43   $695.45   $695.50