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 $92.82   6.499%   $98.8524   $98.85   $98.85   $98.90  
  Purchase #2 $240.65   11.502%   $268.3296   $268.33   $268.35   $268.30  
  Purchase #3 $26.45   7.427%   $28.4144   $28.41   $28.40   $28.40  
  Purchase #4 $210.69   4.189%   $219.5158   $219.52   $219.50   $219.50  
  Purchase #5 $125.68   6.516%   $133.8693   $133.87   $133.85   $133.90  
  Purchase #6 $92.85   5.254%   $97.7283   $97.73   $97.75   $97.70  
  Purchase #7 $233.39   9.119%   $254.6728   $254.67   $254.65   $254.70  
  7 purchase totals = $1,022.53       $1,101.3826   $1,101.38   $1,101.35   $1,101.40