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 $69.30   8.501%   $75.1912   $75.19   $75.20   $75.20  
  Purchase #2 $139.55   7.349%   $149.8055   $149.81   $149.80   $149.80  
  Purchase #3 $48.59   13.370%   $55.0865   $55.09   $55.10   $55.10  
  Purchase #4 $53.85   12.595%   $60.6324   $60.63   $60.65   $60.60  
  Purchase #5 $58.66   7.295%   $62.9392   $62.94   $62.95   $62.90  
  Purchase #6 $112.71   5.493%   $118.9012   $118.90   $118.90   $118.90  
  Purchase #7 $231.50   7.291%   $248.3787   $248.38   $248.40   $248.40  
  7 purchase totals = $714.16       $770.9347   $770.94   $771.00   $770.90