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 $12.63   13.711%   $14.3617   $14.36   $14.35   $14.40  
  Purchase #2 $167.37   3.664%   $173.5024   $173.50   $173.50   $173.50  
  Purchase #3 $153.48   11.362%   $170.9184   $170.92   $170.90   $170.90  
  Purchase #4 $214.83   8.138%   $232.3129   $232.31   $232.30   $232.30  
  Purchase #5 $234.96   7.725%   $253.1107   $253.11   $253.10   $253.10  
  Purchase #6 $211.51   12.395%   $237.7267   $237.73   $237.75   $237.70  
  Purchase #7 $17.96   13.627%   $20.4074   $20.41   $20.40   $20.40  
  7 purchase totals = $1,012.74       $1,102.3402   $1,102.34   $1,102.30   $1,102.30