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 $215.85   4.859%   $226.3382   $226.34   $226.35   $226.30  
  Purchase #2 $45.53   11.596%   $50.8097   $50.81   $50.80   $50.80  
  Purchase #3 $68.82   11.507%   $76.7391   $76.74   $76.75   $76.70  
  Purchase #4 $164.74   7.288%   $176.7463   $176.75   $176.75   $176.70  
  Purchase #5 $76.26   7.615%   $82.0672   $82.07   $82.05   $82.10  
  Purchase #6 $212.94   13.483%   $241.6507   $241.65   $241.65   $241.70  
  Purchase #7 $158.94   7.549%   $170.9384   $170.94   $170.95   $170.90  
  7 purchase totals = $943.08       $1,025.2896   $1,025.30   $1,025.30   $1,025.20