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 $84.82   9.200%   $92.6234   $92.62   $92.60   $92.60  
  Purchase #2 $192.97   6.612%   $205.7292   $205.73   $205.75   $205.70  
  Purchase #3 $22.32   13.309%   $25.2906   $25.29   $25.30   $25.30  
  Purchase #4 $242.84   7.654%   $261.427   $261.43   $261.45   $261.40  
  Purchase #5 $244.27   5.332%   $257.2945   $257.29   $257.30   $257.30  
  Purchase #6 $12.69   7.415%   $13.631   $13.63   $13.65   $13.60  
  Purchase #7 $11.77   11.527%   $13.1267   $13.13   $13.15   $13.10  
  7 purchase totals = $811.68       $869.1224   $869.12   $869.20   $869.00