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 $146.43   5.168%   $153.9975   $154.00   $154.00   $154.00  
  Purchase #2 $60.25   4.869%   $63.1836   $63.18   $63.20   $63.20  
  Purchase #3 $238.60   10.121%   $262.7487   $262.75   $262.75   $262.70  
  Purchase #4 $239.87   8.177%   $259.4842   $259.48   $259.50   $259.50  
  Purchase #5 $175.87   9.714%   $192.954   $192.95   $192.95   $193.00  
  Purchase #6 $99.56   6.737%   $106.2674   $106.27   $106.25   $106.30  
  Purchase #7 $68.84   10.231%   $75.883   $75.88   $75.90   $75.90  
  7 purchase totals = $1,029.42       $1,114.5184   $1,114.51   $1,114.55   $1,114.60