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 $188.87   4.801%   $197.9376   $197.94   $197.95   $197.90  
  Purchase #2 $203.39   5.566%   $214.7107   $214.71   $214.70   $214.70  
  Purchase #3 $15.98   7.632%   $17.1996   $17.20   $17.20   $17.20  
  Purchase #4 $145.46   8.304%   $157.539   $157.54   $157.55   $157.50  
  Purchase #5 $73.57   5.215%   $77.4067   $77.41   $77.40   $77.40  
  Purchase #6 $34.83   5.136%   $36.6189   $36.62   $36.60   $36.60  
  Purchase #7 $57.38   12.704%   $64.6696   $64.67   $64.65   $64.70  
  7 purchase totals = $719.48       $766.0821   $766.09   $766.05   $766.00