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 $211.79   6.828%   $226.251   $226.25   $226.25   $226.30  
  Purchase #2 $68.45   5.873%   $72.4701   $72.47   $72.45   $72.50  
  Purchase #3 $204.38   4.748%   $214.084   $214.08   $214.10   $214.10  
  Purchase #4 $40.39   10.773%   $44.7412   $44.74   $44.75   $44.70  
  Purchase #5 $227.78   12.219%   $255.6124   $255.61   $255.60   $255.60  
  Purchase #6 $197.27   3.662%   $204.494   $204.49   $204.50   $204.50  
  Purchase #7 $42.98   9.216%   $46.941   $46.94   $46.95   $46.90  
  7 purchase totals = $993.04       $1,064.5937   $1,064.58   $1,064.60   $1,064.60