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 $34.69   8.474%   $37.6296   $37.63   $37.65   $37.60  
  Purchase #2 $98.70   8.772%   $107.358   $107.36   $107.35   $107.40  
  Purchase #3 $12.77   7.554%   $13.7346   $13.73   $13.75   $13.70  
  Purchase #4 $190.89   7.329%   $204.8803   $204.88   $204.90   $204.90  
  Purchase #5 $58.95   8.385%   $63.893   $63.89   $63.90   $63.90  
  Purchase #6 $224.53   11.726%   $250.8584   $250.86   $250.85   $250.90  
  Purchase #7 $197.62   9.298%   $215.9947   $215.99   $216.00   $216.00  
  7 purchase totals = $818.15       $894.3486   $894.34   $894.40   $894.40