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 $62.59   11.212%   $69.6076   $69.61   $69.60   $69.60  
  Purchase #2 $166.47   10.501%   $183.951   $183.95   $183.95   $184.00  
  Purchase #3 $139.84   6.139%   $148.4248   $148.42   $148.40   $148.40  
  Purchase #4 $206.93   7.419%   $222.2821   $222.28   $222.30   $222.30  
  Purchase #5 $8.70   5.796%   $9.2043   $9.20   $9.20   $9.20  
  Purchase #6 $15.57   8.562%   $16.9031   $16.90   $16.90   $16.90  
  Purchase #7 $168.96   10.670%   $186.988   $186.99   $187.00   $187.00  
  7 purchase totals = $769.06       $837.3609   $837.35   $837.35   $837.40