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 $205.28   5.687%   $216.9543   $216.95   $216.95   $217.00  
  Purchase #2 $52.37   3.148%   $54.0186   $54.02   $54.00   $54.00  
  Purchase #3 $205.97   9.121%   $224.7565   $224.76   $224.75   $224.80  
  Purchase #4 $19.49   3.470%   $20.1663   $20.17   $20.15   $20.20  
  Purchase #5 $105.36   13.382%   $119.4593   $119.46   $119.45   $119.50  
  Purchase #6 $210.31   4.864%   $220.5395   $220.54   $220.55   $220.50  
  Purchase #7 $89.89   6.187%   $95.4515   $95.45   $95.45   $95.50  
  7 purchase totals = $888.67       $951.3460   $951.35   $951.30   $951.50