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 $157.32   11.842%   $175.9498   $175.95   $175.95   $175.90  
  Purchase #2 $57.98   8.231%   $62.7523   $62.75   $62.75   $62.80  
  Purchase #3 $51.55   4.660%   $53.9522   $53.95   $53.95   $54.00  
  Purchase #4 $249.26   10.183%   $274.6421   $274.64   $274.65   $274.60  
  Purchase #5 $62.38   4.742%   $65.3381   $65.34   $65.35   $65.30  
  Purchase #6 $171.71   4.203%   $178.927   $178.93   $178.95   $178.90  
  Purchase #7 $73.82   4.103%   $76.8488   $76.85   $76.85   $76.80  
  7 purchase totals = $824.02       $888.4103   $888.41   $888.45   $888.30