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 $114.68   9.776%   $125.8911   $125.89   $125.90   $125.90  
  Purchase #2 $160.31   3.128%   $165.3245   $165.32   $165.30   $165.30  
  Purchase #3 $55.25   9.765%   $60.6452   $60.65   $60.65   $60.60  
  Purchase #4 $232.51   4.507%   $242.9892   $242.99   $243.00   $243.00  
  Purchase #5 $101.53   4.308%   $105.9039   $105.90   $105.90   $105.90  
  Purchase #6 $19.57   10.490%   $21.6229   $21.62   $21.60   $21.60  
  Purchase #7 $14.46   7.600%   $15.559   $15.56   $15.55   $15.60  
  7 purchase totals = $698.31       $737.9358   $737.93   $737.90   $737.90