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 $243.78   7.455%   $261.9538   $261.95   $261.95   $262.00  
  Purchase #2 $195.73   8.818%   $212.9895   $212.99   $213.00   $213.00  
  Purchase #3 $171.30   6.854%   $183.0409   $183.04   $183.05   $183.00  
  Purchase #4 $158.31   12.774%   $178.5325   $178.53   $178.55   $178.50  
  Purchase #5 $224.45   3.321%   $231.904   $231.90   $231.90   $231.90  
  Purchase #6 $216.65   12.617%   $243.9847   $243.98   $244.00   $244.00  
  Purchase #7 $131.54   5.614%   $138.9247   $138.92   $138.90   $138.90  
  7 purchase totals = $1,341.76       $1,451.3301   $1,451.31   $1,451.35   $1,451.30