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 $72.81   5.196%   $76.5932   $76.59   $76.60   $76.60  
  Purchase #2 $206.43   9.182%   $225.3844   $225.38   $225.40   $225.40  
  Purchase #3 $61.90   8.694%   $67.2816   $67.28   $67.30   $67.30  
  Purchase #4 $240.29   8.814%   $261.4692   $261.47   $261.45   $261.50  
  Purchase #5 $148.53   12.412%   $166.9655   $166.97   $166.95   $167.00  
  Purchase #6 $247.74   10.671%   $274.1763   $274.18   $274.20   $274.20  
  Purchase #7 $10.64   12.264%   $11.9449   $11.94   $11.95   $11.90  
  7 purchase totals = $988.34       $1,083.8151   $1,083.81   $1,083.85   $1,083.90