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 $44.58   5.166%   $46.883   $46.88   $46.90   $46.90  
  Purchase #2 $87.89   12.451%   $98.8332   $98.83   $98.85   $98.80  
  Purchase #3 $107.68   4.865%   $112.9186   $112.92   $112.90   $112.90  
  Purchase #4 $54.62   7.171%   $58.5368   $58.54   $58.55   $58.50  
  Purchase #5 $107.38   11.429%   $119.6525   $119.65   $119.65   $119.70  
  Purchase #6 $200.30   10.754%   $221.8403   $221.84   $221.85   $221.80  
  Purchase #7 $242.52   5.779%   $256.5352   $256.54   $256.55   $256.50  
  7 purchase totals = $844.97       $915.1996   $915.20   $915.25   $915.10