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 $67.41   3.790%   $69.9648   $69.96   $69.95   $70.00  
  Purchase #2 $177.86   12.294%   $199.7261   $199.73   $199.75   $199.70  
  Purchase #3 $219.96   7.360%   $236.1491   $236.15   $236.15   $236.10  
  Purchase #4 $12.99   7.727%   $13.9937   $13.99   $14.00   $14.00  
  Purchase #5 $211.93   4.607%   $221.6936   $221.69   $221.70   $221.70  
  Purchase #6 $146.30   11.621%   $163.3015   $163.30   $163.30   $163.30  
  Purchase #7 $5.75   12.480%   $6.4676   $6.47   $6.45   $6.50  
  7 purchase totals = $842.20       $911.2964   $911.29   $911.30   $911.30