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 $183.39   6.464%   $195.2443   $195.24   $195.25   $195.20  
  Purchase #2 $122.91   11.170%   $136.639   $136.64   $136.65   $136.60  
  Purchase #3 $8.87   4.504%   $9.2695   $9.27   $9.25   $9.30  
  Purchase #4 $111.31   6.428%   $118.465   $118.47   $118.45   $118.50  
  Purchase #5 $93.29   9.251%   $101.9203   $101.92   $101.90   $101.90  
  Purchase #6 $216.94   8.573%   $235.5383   $235.54   $235.55   $235.50  
  Purchase #7 $193.98   12.243%   $217.729   $217.73   $217.75   $217.70  
  7 purchase totals = $930.69       $1,014.8054   $1,014.81   $1,014.80   $1,014.70