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 $192.76   11.868%   $215.6368   $215.64   $215.65   $215.60  
  Purchase #2 $69.34   3.345%   $71.6594   $71.66   $71.65   $71.70  
  Purchase #3 $244.58   6.805%   $261.2237   $261.22   $261.20   $261.20  
  Purchase #4 $216.93   4.679%   $227.0802   $227.08   $227.10   $227.10  
  Purchase #5 $95.98   3.213%   $99.0638   $99.06   $99.05   $99.10  
  Purchase #6 $53.73   6.141%   $57.0296   $57.03   $57.05   $57.00  
  Purchase #7 $76.33   7.805%   $82.2876   $82.29   $82.30   $82.30  
  7 purchase totals = $949.65       $1,013.9811   $1,013.98   $1,014.00   $1,014.00