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 $209.80   13.278%   $237.6572   $237.66   $237.65   $237.70  
  Purchase #2 $54.82   3.334%   $56.6477   $56.65   $56.65   $56.60  
  Purchase #3 $57.64   7.117%   $61.7422   $61.74   $61.75   $61.70  
  Purchase #4 $68.96   11.124%   $76.6311   $76.63   $76.65   $76.60  
  Purchase #5 $145.49   8.360%   $157.653   $157.65   $157.65   $157.70  
  Purchase #6 $82.56   4.859%   $86.5716   $86.57   $86.55   $86.60  
  Purchase #7 $141.64   9.499%   $155.0944   $155.09   $155.10   $155.10  
  7 purchase totals = $760.91       $831.9972   $831.99   $832.00   $832.00