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 $54.53   11.819%   $60.9749   $60.97   $60.95   $61.00  
  Purchase #2 $48.80   11.767%   $54.5423   $54.54   $54.55   $54.50  
  Purchase #3 $245.53   4.323%   $256.1443   $256.14   $256.15   $256.10  
  Purchase #4 $206.59   8.501%   $224.1522   $224.15   $224.15   $224.20  
  Purchase #5 $116.39   7.646%   $125.2892   $125.29   $125.30   $125.30  
  Purchase #6 $81.82   12.316%   $91.897   $91.90   $91.90   $91.90  
  Purchase #7 $230.61   10.538%   $254.9117   $254.91   $254.90   $254.90  
  7 purchase totals = $984.27       $1,067.9116   $1,067.90   $1,067.90   $1,067.90