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 $215.95   7.495%   $232.1355   $232.14   $232.15   $232.10  
  Purchase #2 $61.97   6.261%   $65.8499   $65.85   $65.85   $65.80  
  Purchase #3 $108.81   11.198%   $120.9945   $120.99   $121.00   $121.00  
  Purchase #4 $184.63   5.568%   $194.9102   $194.91   $194.90   $194.90  
  Purchase #5 $190.93   8.113%   $206.4202   $206.42   $206.40   $206.40  
  Purchase #6 $41.93   10.784%   $46.4517   $46.45   $46.45   $46.50  
  Purchase #7 $168.70   5.597%   $178.1421   $178.14   $178.15   $178.10  
  7 purchase totals = $972.92       $1,044.9041   $1,044.90   $1,044.90   $1,044.80