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 $215.77   5.193%   $226.9749   $226.97   $226.95   $227.00  
  Purchase #2 $119.93   6.660%   $127.9173   $127.92   $127.90   $127.90  
  Purchase #3 $13.94   4.783%   $14.6068   $14.61   $14.60   $14.60  
  Purchase #4 $160.63   12.135%   $180.1225   $180.12   $180.10   $180.10  
  Purchase #5 $204.83   4.136%   $213.3018   $213.30   $213.30   $213.30  
  Purchase #6 $39.75   4.313%   $41.4644   $41.46   $41.45   $41.50  
  Purchase #7 $238.43   7.334%   $255.9165   $255.92   $255.90   $255.90  
  7 purchase totals = $993.28       $1,060.3042   $1,060.30   $1,060.20   $1,060.30