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 $217.32   7.507%   $233.6342   $233.63   $233.65   $233.60  
  Purchase #2 $233.74   4.487%   $244.2279   $244.23   $244.25   $244.20  
  Purchase #3 $98.43   4.634%   $102.9912   $102.99   $103.00   $103.00  
  Purchase #4 $22.94   4.728%   $24.0246   $24.02   $24.00   $24.00  
  Purchase #5 $109.97   12.335%   $123.5348   $123.53   $123.55   $123.50  
  Purchase #6 $64.88   3.494%   $67.1469   $67.15   $67.15   $67.10  
  Purchase #7 $241.62   6.802%   $258.055   $258.06   $258.05   $258.10  
  7 purchase totals = $988.90       $1,053.6146   $1,053.61   $1,053.65   $1,053.50