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 $213.27   6.413%   $226.947   $226.95   $226.95   $226.90  
  Purchase #2 $244.63   3.845%   $254.036   $254.04   $254.05   $254.00  
  Purchase #3 $19.33   5.700%   $20.4318   $20.43   $20.45   $20.40  
  Purchase #4 $152.53   12.716%   $171.9257   $171.93   $171.95   $171.90  
  Purchase #5 $238.77   9.607%   $261.7086   $261.71   $261.70   $261.70  
  Purchase #6 $142.90   12.144%   $160.2538   $160.25   $160.25   $160.30  
  Purchase #7 $155.40   3.596%   $160.9882   $160.99   $161.00   $161.00  
  7 purchase totals = $1,166.83       $1,256.2911   $1,256.30   $1,256.35   $1,256.20