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 $46.66   3.656%   $48.3659   $48.37   $48.35   $48.40  
  Purchase #2 $200.91   12.659%   $226.3432   $226.34   $226.35   $226.30  
  Purchase #3 $25.58   6.603%   $27.269   $27.27   $27.25   $27.30  
  Purchase #4 $176.53   4.395%   $184.2885   $184.29   $184.30   $184.30  
  Purchase #5 $148.92   8.186%   $161.1106   $161.11   $161.10   $161.10  
  Purchase #6 $111.94   9.238%   $122.281   $122.28   $122.30   $122.30  
  Purchase #7 $185.55   4.209%   $193.3598   $193.36   $193.35   $193.40  
  7 purchase totals = $896.09       $963.0180   $963.02   $963.00   $963.10