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 $195.97   8.562%   $212.749   $212.75   $212.75   $212.70  
  Purchase #2 $61.86   4.863%   $64.8683   $64.87   $64.85   $64.90  
  Purchase #3 $126.84   13.739%   $144.2665   $144.27   $144.25   $144.30  
  Purchase #4 $211.27   10.499%   $233.4512   $233.45   $233.45   $233.50  
  Purchase #5 $62.75   12.559%   $70.6308   $70.63   $70.65   $70.60  
  Purchase #6 $207.34   13.403%   $235.1298   $235.13   $235.15   $235.10  
  Purchase #7 $204.91   8.209%   $221.7311   $221.73   $221.75   $221.70  
  7 purchase totals = $1,070.94       $1,182.8267   $1,182.83   $1,182.85   $1,182.80