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 $44.94   3.844%   $46.6675   $46.67   $46.65   $46.70  
  Purchase #2 $196.54   8.163%   $212.5836   $212.58   $212.60   $212.60  
  Purchase #3 $154.87   11.153%   $172.1427   $172.14   $172.15   $172.10  
  Purchase #4 $12.31   4.665%   $12.8843   $12.88   $12.90   $12.90  
  Purchase #5 $191.68   10.154%   $211.1432   $211.14   $211.15   $211.10  
  Purchase #6 $33.91   3.473%   $35.0877   $35.09   $35.10   $35.10  
  Purchase #7 $24.76   3.504%   $25.6276   $25.63   $25.65   $25.60  
  7 purchase totals = $659.01       $716.1366   $716.13   $716.20   $716.10