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 $46.89   11.219%   $52.1506   $52.15   $52.15   $52.20  
  Purchase #2 $216.98   8.399%   $235.2042   $235.20   $235.20   $235.20  
  Purchase #3 $88.78   8.494%   $96.321   $96.32   $96.30   $96.30  
  Purchase #4 $71.91   5.846%   $76.1139   $76.11   $76.10   $76.10  
  Purchase #5 $76.77   3.227%   $79.2474   $79.25   $79.25   $79.20  
  Purchase #6 $196.25   13.274%   $222.3002   $222.30   $222.30   $222.30  
  Purchase #7 $119.56   12.184%   $134.1272   $134.13   $134.15   $134.10  
  7 purchase totals = $817.14       $895.4645   $895.46   $895.45   $895.40