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 $60.25   12.786%   $67.9536   $67.95   $67.95   $68.00  
  Purchase #2 $213.40   9.482%   $233.6346   $233.63   $233.65   $233.60  
  Purchase #3 $163.68   10.458%   $180.7977   $180.80   $180.80   $180.80  
  Purchase #4 $19.39   10.273%   $21.3819   $21.38   $21.40   $21.40  
  Purchase #5 $185.35   4.369%   $193.4479   $193.45   $193.45   $193.40  
  Purchase #6 $9.99   11.804%   $11.1692   $11.17   $11.15   $11.20  
  Purchase #7 $223.26   3.873%   $231.9069   $231.91   $231.90   $231.90  
  7 purchase totals = $875.32       $940.2918   $940.29   $940.30   $940.30