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 $62.95   4.815%   $65.981   $65.98   $66.00   $66.00  
  Purchase #2 $227.80   5.408%   $240.1194   $240.12   $240.10   $240.10  
  Purchase #3 $21.90   13.615%   $24.8817   $24.88   $24.90   $24.90  
  Purchase #4 $16.76   13.194%   $18.9713   $18.97   $18.95   $19.00  
  Purchase #5 $161.53   3.187%   $166.678   $166.68   $166.70   $166.70  
  Purchase #6 $181.83   6.219%   $193.138   $193.14   $193.15   $193.10  
  Purchase #7 $45.71   7.868%   $49.3065   $49.31   $49.30   $49.30  
  7 purchase totals = $718.48       $759.0759   $759.08   $759.10   $759.10