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 $223.53   10.618%   $247.2644   $247.26   $247.25   $247.30  
  Purchase #2 $246.66   5.316%   $259.7724   $259.77   $259.75   $259.80  
  Purchase #3 $10.28   6.769%   $10.9759   $10.98   $11.00   $11.00  
  Purchase #4 $216.76   7.650%   $233.3421   $233.34   $233.35   $233.30  
  Purchase #5 $235.38   5.350%   $247.9728   $247.97   $247.95   $248.00  
  Purchase #6 $94.74   11.339%   $105.4826   $105.48   $105.50   $105.50  
  Purchase #7 $92.31   7.581%   $99.308   $99.31   $99.30   $99.30  
  7 purchase totals = $1,119.66       $1,204.1182   $1,204.11   $1,204.10   $1,204.20