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 $61.54   5.852%   $65.1413   $65.14   $65.15   $65.10  
  Purchase #2 $248.34   5.561%   $262.1502   $262.15   $262.15   $262.20  
  Purchase #3 $246.90   11.641%   $275.6416   $275.64   $275.65   $275.60  
  Purchase #4 $209.40   6.603%   $223.2267   $223.23   $223.25   $223.20  
  Purchase #5 $126.98   8.559%   $137.8482   $137.85   $137.85   $137.80  
  Purchase #6 $213.49   9.571%   $233.9231   $233.92   $233.90   $233.90  
  Purchase #7 $101.69   5.551%   $107.3348   $107.33   $107.35   $107.30  
  7 purchase totals = $1,208.34       $1,305.2659   $1,305.26   $1,305.30   $1,305.10