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 $32.82   3.785%   $34.0622   $34.06   $34.05   $34.10  
  Purchase #2 $183.42   7.591%   $197.3434   $197.34   $197.35   $197.30  
  Purchase #3 $117.66   4.708%   $123.1994   $123.20   $123.20   $123.20  
  Purchase #4 $216.85   3.520%   $224.4831   $224.48   $224.50   $224.50  
  Purchase #5 $173.95   11.375%   $193.7368   $193.74   $193.75   $193.70  
  Purchase #6 $229.26   5.718%   $242.3691   $242.37   $242.35   $242.40  
  Purchase #7 $143.33   5.458%   $151.153   $151.15   $151.15   $151.20  
  7 purchase totals = $1,097.29       $1,166.3470   $1,166.34   $1,166.35   $1,166.40