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 $104.48   7.707%   $112.5323   $112.53   $112.55   $112.50  
  Purchase #2 $226.57   4.698%   $237.2143   $237.21   $237.20   $237.20  
  Purchase #3 $152.62   12.616%   $171.8745   $171.87   $171.85   $171.90  
  Purchase #4 $250.97   10.164%   $276.4786   $276.48   $276.50   $276.50  
  Purchase #5 $151.96   5.427%   $160.2069   $160.21   $160.20   $160.20  
  Purchase #6 $230.28   8.481%   $249.81   $249.81   $249.80   $249.80  
  Purchase #7 $221.74   10.130%   $244.2023   $244.20   $244.20   $244.20  
  7 purchase totals = $1,338.62       $1,452.3189   $1,452.31   $1,452.30   $1,452.30