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 $214.39   5.674%   $226.5545   $226.55   $226.55   $226.60  
  Purchase #2 $8.90   8.739%   $9.6778   $9.68   $9.70   $9.70  
  Purchase #3 $52.97   5.455%   $55.8595   $55.86   $55.85   $55.90  
  Purchase #4 $96.76   4.804%   $101.4084   $101.41   $101.40   $101.40  
  Purchase #5 $204.96   3.332%   $211.7893   $211.79   $211.80   $211.80  
  Purchase #6 $126.85   10.501%   $140.1705   $140.17   $140.15   $140.20  
  Purchase #7 $158.63   5.745%   $167.7433   $167.74   $167.75   $167.70  
  7 purchase totals = $863.46       $913.2033   $913.20   $913.20   $913.30