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 $164.94   5.348%   $173.761   $173.76   $173.75   $173.80  
  Purchase #2 $243.70   6.545%   $259.6502   $259.65   $259.65   $259.70  
  Purchase #3 $197.38   5.417%   $208.0721   $208.07   $208.05   $208.10  
  Purchase #4 $164.74   3.648%   $170.7497   $170.75   $170.75   $170.70  
  Purchase #5 $85.29   8.213%   $92.2949   $92.29   $92.30   $92.30  
  Purchase #6 $91.34   11.635%   $101.9674   $101.97   $101.95   $102.00  
  Purchase #7 $51.76   3.791%   $53.7222   $53.72   $53.70   $53.70  
  7 purchase totals = $999.15       $1,060.2175   $1,060.21   $1,060.15   $1,060.30