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 $177.41   10.242%   $195.5803   $195.58   $195.60   $195.60  
  Purchase #2 $186.73   5.568%   $197.1271   $197.13   $197.15   $197.10  
  Purchase #3 $128.76   11.605%   $143.7026   $143.70   $143.70   $143.70  
  Purchase #4 $66.87   3.605%   $69.2807   $69.28   $69.30   $69.30  
  Purchase #5 $245.53   3.296%   $253.6227   $253.62   $253.60   $253.60  
  Purchase #6 $12.66   10.389%   $13.9752   $13.98   $14.00   $14.00  
  Purchase #7 $133.78   7.807%   $144.2242   $144.22   $144.20   $144.20  
  7 purchase totals = $951.74       $1,017.5128   $1,017.51   $1,017.55   $1,017.50