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 $22.92   7.389%   $24.6136   $24.61   $24.60   $24.60  
  Purchase #2 $171.31   13.725%   $194.8223   $194.82   $194.80   $194.80  
  Purchase #3 $144.99   9.131%   $158.229   $158.23   $158.25   $158.20  
  Purchase #4 $169.68   6.849%   $181.3014   $181.30   $181.30   $181.30  
  Purchase #5 $124.29   10.188%   $136.9527   $136.95   $136.95   $137.00  
  Purchase #6 $234.64   11.745%   $262.1985   $262.20   $262.20   $262.20  
  Purchase #7 $203.62   10.270%   $224.5318   $224.53   $224.55   $224.50  
  7 purchase totals = $1,071.45       $1,182.6493   $1,182.64   $1,182.65   $1,182.60