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 $214.60   12.639%   $241.7233   $241.72   $241.70   $241.70  
  Purchase #2 $67.95   10.798%   $75.2872   $75.29   $75.30   $75.30  
  Purchase #3 $167.95   4.382%   $175.3096   $175.31   $175.30   $175.30  
  Purchase #4 $73.84   3.571%   $76.4768   $76.48   $76.50   $76.50  
  Purchase #5 $215.43   13.814%   $245.1895   $245.19   $245.20   $245.20  
  Purchase #6 $159.28   7.676%   $171.5063   $171.51   $171.50   $171.50  
  Purchase #7 $236.26   3.397%   $244.2858   $244.29   $244.30   $244.30  
  7 purchase totals = $1,135.31       $1,229.7785   $1,229.79   $1,229.80   $1,229.80