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 $48.26   11.814%   $53.9614   $53.96   $53.95   $54.00  
  Purchase #2 $188.74   8.299%   $204.4035   $204.40   $204.40   $204.40  
  Purchase #3 $127.64   6.317%   $135.703   $135.70   $135.70   $135.70  
  Purchase #4 $180.80   10.161%   $199.1711   $199.17   $199.15   $199.20  
  Purchase #5 $239.44   11.117%   $266.0585   $266.06   $266.05   $266.10  
  Purchase #6 $52.35   5.446%   $55.201   $55.20   $55.20   $55.20  
  Purchase #7 $27.78   10.754%   $30.7675   $30.77   $30.75   $30.80  
  7 purchase totals = $865.01       $945.2660   $945.26   $945.20   $945.40