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 $177.32   11.133%   $197.061   $197.06   $197.05   $197.10  
  Purchase #2 $235.85   9.403%   $258.027   $258.03   $258.05   $258.00  
  Purchase #3 $250.61   10.408%   $276.6935   $276.69   $276.70   $276.70  
  Purchase #4 $19.49   11.628%   $21.7563   $21.76   $21.75   $21.80  
  Purchase #5 $10.92   12.766%   $12.314   $12.31   $12.30   $12.30  
  Purchase #6 $194.38   6.641%   $207.2888   $207.29   $207.30   $207.30  
  Purchase #7 $67.65   13.431%   $76.7361   $76.74   $76.75   $76.70  
  7 purchase totals = $956.22       $1,049.8767   $1,049.88   $1,049.90   $1,049.90