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 $241.32   5.526%   $254.6553   $254.66   $254.65   $254.70  
  Purchase #2 $119.65   4.872%   $125.4793   $125.48   $125.50   $125.50  
  Purchase #3 $148.26   7.350%   $159.1571   $159.16   $159.15   $159.20  
  Purchase #4 $242.26   8.460%   $262.7552   $262.76   $262.75   $262.80  
  Purchase #5 $156.97   4.240%   $163.6255   $163.63   $163.65   $163.60  
  Purchase #6 $109.91   11.558%   $122.6134   $122.61   $122.60   $122.60  
  Purchase #7 $96.59   10.346%   $106.5832   $106.58   $106.60   $106.60  
  7 purchase totals = $1,114.96       $1,194.8690   $1,194.88   $1,194.90   $1,195.00