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 $179.62   9.804%   $197.2299   $197.23   $197.25   $197.20  
  Purchase #2 $83.48   4.572%   $87.2967   $87.30   $87.30   $87.30  
  Purchase #3 $142.44   4.486%   $148.8299   $148.83   $148.85   $148.80  
  Purchase #4 $238.66   6.805%   $254.9008   $254.90   $254.90   $254.90  
  Purchase #5 $136.49   5.463%   $143.9464   $143.95   $143.95   $143.90  
  Purchase #6 $108.83   5.562%   $114.8831   $114.88   $114.90   $114.90  
  Purchase #7 $61.56   4.356%   $64.2416   $64.24   $64.25   $64.20  
  7 purchase totals = $951.08       $1,011.3284   $1,011.33   $1,011.40   $1,011.20