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 $232.33   6.576%   $247.608   $247.61   $247.60   $247.60  
  Purchase #2 $48.50   5.782%   $51.3043   $51.30   $51.30   $51.30  
  Purchase #3 $115.79   10.353%   $127.7777   $127.78   $127.80   $127.80  
  Purchase #4 $166.88   9.325%   $182.4416   $182.44   $182.45   $182.40  
  Purchase #5 $91.27   7.524%   $98.1372   $98.14   $98.15   $98.10  
  Purchase #6 $71.47   7.557%   $76.871   $76.87   $76.85   $76.90  
  Purchase #7 $142.88   13.364%   $161.9745   $161.97   $161.95   $162.00  
  7 purchase totals = $869.12       $946.1143   $946.11   $946.10   $946.10