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 $57.61   5.794%   $60.9479   $60.95   $60.95   $60.90  
  Purchase #2 $91.66   10.668%   $101.4383   $101.44   $101.45   $101.40  
  Purchase #3 $238.82   8.555%   $259.2511   $259.25   $259.25   $259.30  
  Purchase #4 $34.76   3.431%   $35.9526   $35.95   $35.95   $36.00  
  Purchase #5 $246.34   6.538%   $262.4457   $262.45   $262.45   $262.40  
  Purchase #6 $159.90   4.656%   $167.3449   $167.34   $167.35   $167.30  
  Purchase #7 $226.92   8.134%   $245.3777   $245.38   $245.40   $245.40  
  7 purchase totals = $1,056.01       $1,132.7582   $1,132.76   $1,132.80   $1,132.70