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 $43.37   8.533%   $47.0708   $47.07   $47.05   $47.10  
  Purchase #2 $170.79   8.289%   $184.9468   $184.95   $184.95   $184.90  
  Purchase #3 $166.85   5.804%   $176.534   $176.53   $176.55   $176.50  
  Purchase #4 $44.73   3.401%   $46.2513   $46.25   $46.25   $46.30  
  Purchase #5 $188.92   13.385%   $214.2069   $214.21   $214.20   $214.20  
  Purchase #6 $173.49   7.694%   $186.8383   $186.84   $186.85   $186.80  
  Purchase #7 $93.87   9.751%   $103.0233   $103.02   $103.00   $103.00  
  7 purchase totals = $882.02       $958.8714   $958.87   $958.85   $958.80