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 $68.93   7.276%   $73.9453   $73.95   $73.95   $73.90  
  Purchase #2 $125.65   7.428%   $134.9833   $134.98   $135.00   $135.00  
  Purchase #3 $148.70   9.266%   $162.4785   $162.48   $162.50   $162.50  
  Purchase #4 $231.79   7.223%   $248.5322   $248.53   $248.55   $248.50  
  Purchase #5 $238.30   5.725%   $251.9427   $251.94   $251.95   $251.90  
  Purchase #6 $94.87   6.136%   $100.6912   $100.69   $100.70   $100.70  
  Purchase #7 $42.99   8.171%   $46.5027   $46.50   $46.50   $46.50  
  7 purchase totals = $951.23       $1,019.0759   $1,019.07   $1,019.15   $1,019.00