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 $84.71   9.129%   $92.4432   $92.44   $92.45   $92.40  
  Purchase #2 $81.47   13.828%   $92.7357   $92.74   $92.75   $92.70  
  Purchase #3 $231.79   6.827%   $247.6143   $247.61   $247.60   $247.60  
  Purchase #4 $236.56   6.843%   $252.7478   $252.75   $252.75   $252.70  
  Purchase #5 $48.82   11.267%   $54.3205   $54.32   $54.30   $54.30  
  Purchase #6 $228.87   11.230%   $254.5721   $254.57   $254.55   $254.60  
  Purchase #7 $47.75   5.605%   $50.4264   $50.43   $50.45   $50.40  
  7 purchase totals = $959.97       $1,044.8600   $1,044.86   $1,044.85   $1,044.70