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 $72.38   5.262%   $76.1886   $76.19   $76.20   $76.20  
  Purchase #2 $153.92   6.452%   $163.8509   $163.85   $163.85   $163.90  
  Purchase #3 $116.89   6.406%   $124.378   $124.38   $124.40   $124.40  
  Purchase #4 $212.53   5.835%   $224.9311   $224.93   $224.95   $224.90  
  Purchase #5 $106.64   10.340%   $117.6666   $117.67   $117.65   $117.70  
  Purchase #6 $221.94   10.587%   $245.4368   $245.44   $245.45   $245.40  
  Purchase #7 $185.61   7.302%   $199.1632   $199.16   $199.15   $199.20  
  7 purchase totals = $1,069.91       $1,151.6152   $1,151.62   $1,151.65   $1,151.70