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 $195.63   5.566%   $206.5188   $206.52   $206.50   $206.50  
  Purchase #2 $175.59   12.568%   $197.6582   $197.66   $197.65   $197.70  
  Purchase #3 $237.45   10.145%   $261.5393   $261.54   $261.55   $261.50  
  Purchase #4 $108.34   9.789%   $118.9454   $118.95   $118.95   $118.90  
  Purchase #5 $28.87   5.744%   $30.5283   $30.53   $30.55   $30.50  
  Purchase #6 $134.61   8.420%   $145.9442   $145.94   $145.95   $145.90  
  Purchase #7 $223.91   8.674%   $243.332   $243.33   $243.35   $243.30  
  7 purchase totals = $1,104.40       $1,204.4662   $1,204.47   $1,204.50   $1,204.30