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 $196.61   9.741%   $215.7618   $215.76   $215.75   $215.80  
  Purchase #2 $34.47   9.287%   $37.6712   $37.67   $37.65   $37.70  
  Purchase #3 $174.53   10.774%   $193.3339   $193.33   $193.35   $193.30  
  Purchase #4 $136.74   5.571%   $144.3578   $144.36   $144.35   $144.40  
  Purchase #5 $183.92   7.441%   $197.6055   $197.61   $197.60   $197.60  
  Purchase #6 $43.56   7.486%   $46.8209   $46.82   $46.80   $46.80  
  Purchase #7 $99.59   10.634%   $110.1804   $110.18   $110.20   $110.20  
  7 purchase totals = $869.42       $945.7315   $945.73   $945.70   $945.80