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 $173.90   12.272%   $195.241   $195.24   $195.25   $195.20  
  Purchase #2 $51.58   5.338%   $54.3333   $54.33   $54.35   $54.30  
  Purchase #3 $118.37   12.634%   $133.3249   $133.32   $133.30   $133.30  
  Purchase #4 $161.53   3.754%   $167.5938   $167.59   $167.60   $167.60  
  Purchase #5 $70.88   9.845%   $77.8581   $77.86   $77.85   $77.90  
  Purchase #6 $98.25   8.274%   $106.3792   $106.38   $106.40   $106.40  
  Purchase #7 $21.91   7.117%   $23.4693   $23.47   $23.45   $23.50  
  7 purchase totals = $696.42       $758.1996   $758.19   $758.20   $758.20