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 $61.44   10.267%   $67.748   $67.75   $67.75   $67.70  
  Purchase #2 $153.45   9.276%   $167.684   $167.68   $167.70   $167.70  
  Purchase #3 $13.58   13.109%   $15.3602   $15.36   $15.35   $15.40  
  Purchase #4 $85.72   13.531%   $97.3188   $97.32   $97.30   $97.30  
  Purchase #5 $162.87   4.844%   $170.7594   $170.76   $170.75   $170.80  
  Purchase #6 $37.61   12.557%   $42.3327   $42.33   $42.35   $42.30  
  Purchase #7 $195.70   9.717%   $214.7162   $214.72   $214.70   $214.70  
  7 purchase totals = $710.37       $775.9193   $775.92   $775.90   $775.90