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 $90.87   4.572%   $95.0246   $95.02   $95.00   $95.00  
  Purchase #2 $166.62   9.353%   $182.204   $182.20   $182.20   $182.20  
  Purchase #3 $151.33   10.787%   $167.654   $167.65   $167.65   $167.70  
  Purchase #4 $156.39   13.733%   $177.867   $177.87   $177.85   $177.90  
  Purchase #5 $227.87   13.737%   $259.1725   $259.17   $259.15   $259.20  
  Purchase #6 $9.59   9.650%   $10.5154   $10.52   $10.50   $10.50  
  Purchase #7 $122.72   11.845%   $137.2562   $137.26   $137.25   $137.30  
  7 purchase totals = $925.39       $1,029.6937   $1,029.69   $1,029.60   $1,029.80