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 $44.98   3.483%   $46.5467   $46.55   $46.55   $46.50  
  Purchase #2 $124.66   13.183%   $141.0939   $141.09   $141.10   $141.10  
  Purchase #3 $193.78   11.322%   $215.7198   $215.72   $215.70   $215.70  
  Purchase #4 $117.35   3.313%   $121.2378   $121.24   $121.25   $121.20  
  Purchase #5 $72.76   9.740%   $79.8468   $79.85   $79.85   $79.80  
  Purchase #6 $144.38   11.693%   $161.2624   $161.26   $161.25   $161.30  
  Purchase #7 $104.97   11.218%   $116.7455   $116.75   $116.75   $116.70  
  7 purchase totals = $802.88       $882.4529   $882.46   $882.45   $882.30