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 $90.82   4.220%   $94.6526   $94.65   $94.65   $94.70  
  Purchase #2 $190.57   11.849%   $213.1506   $213.15   $213.15   $213.20  
  Purchase #3 $53.95   6.546%   $57.4816   $57.48   $57.50   $57.50  
  Purchase #4 $12.97   4.371%   $13.5369   $13.54   $13.55   $13.50  
  Purchase #5 $121.82   3.309%   $125.851   $125.85   $125.85   $125.90  
  Purchase #6 $195.89   5.531%   $206.7247   $206.72   $206.70   $206.70  
  Purchase #7 $201.43   10.273%   $222.1229   $222.12   $222.10   $222.10  
  7 purchase totals = $867.45       $933.5203   $933.51   $933.50   $933.60