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 $184.64   5.664%   $195.098   $195.10   $195.10   $195.10  
  Purchase #2 $49.95   9.513%   $54.7017   $54.70   $54.70   $54.70  
  Purchase #3 $153.43   13.170%   $173.6367   $173.64   $173.65   $173.60  
  Purchase #4 $14.51   9.757%   $15.9257   $15.93   $15.95   $15.90  
  Purchase #5 $194.71   11.566%   $217.2302   $217.23   $217.25   $217.20  
  Purchase #6 $158.76   9.538%   $173.9025   $173.90   $173.90   $173.90  
  Purchase #7 $176.38   10.243%   $194.4466   $194.45   $194.45   $194.40  
  7 purchase totals = $932.38       $1,024.9414   $1,024.95   $1,025.00   $1,024.80