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 $118.94   5.418%   $125.3842   $125.38   $125.40   $125.40  
  Purchase #2 $43.70   9.238%   $47.737   $47.74   $47.75   $47.70  
  Purchase #3 $45.86   4.656%   $47.9952   $48.00   $48.00   $48.00  
  Purchase #4 $64.54   3.455%   $66.7699   $66.77   $66.75   $66.80  
  Purchase #5 $138.55   13.831%   $157.7129   $157.71   $157.70   $157.70  
  Purchase #6 $206.66   7.347%   $221.8433   $221.84   $221.85   $221.80  
  Purchase #7 $237.33   7.381%   $254.8473   $254.85   $254.85   $254.80  
  7 purchase totals = $855.58       $922.2898   $922.29   $922.30   $922.20