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 $223.58   4.762%   $234.2269   $234.23   $234.25   $234.20  
  Purchase #2 $226.98   11.150%   $252.2883   $252.29   $252.30   $252.30  
  Purchase #3 $203.93   8.601%   $221.47   $221.47   $221.45   $221.50  
  Purchase #4 $74.35   6.517%   $79.1954   $79.20   $79.20   $79.20  
  Purchase #5 $240.82   8.793%   $261.9953   $262.00   $262.00   $262.00  
  Purchase #6 $46.93   8.512%   $50.9247   $50.92   $50.90   $50.90  
  Purchase #7 $5.33   4.141%   $5.5507   $5.55   $5.55   $5.60  
  7 purchase totals = $1,021.92       $1,105.6513   $1,105.66   $1,105.65   $1,105.70