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 $55.59   11.463%   $61.9623   $61.96   $61.95   $62.00  
  Purchase #2 $201.32   5.269%   $211.9276   $211.93   $211.95   $211.90  
  Purchase #3 $173.42   13.356%   $196.582   $196.58   $196.60   $196.60  
  Purchase #4 $115.87   8.178%   $125.3458   $125.35   $125.35   $125.30  
  Purchase #5 $208.58   7.607%   $224.4467   $224.45   $224.45   $224.40  
  Purchase #6 $49.70   10.776%   $55.0557   $55.06   $55.05   $55.10  
  Purchase #7 $72.42   10.133%   $79.7583   $79.76   $79.75   $79.80  
  7 purchase totals = $876.90       $955.0784   $955.09   $955.10   $955.10