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 $72.27   5.600%   $76.3171   $76.32   $76.30   $76.30  
  Purchase #2 $110.55   13.263%   $125.2122   $125.21   $125.20   $125.20  
  Purchase #3 $41.46   7.799%   $44.6935   $44.69   $44.70   $44.70  
  Purchase #4 $200.79   3.285%   $207.386   $207.39   $207.40   $207.40  
  Purchase #5 $214.49   4.396%   $223.919   $223.92   $223.90   $223.90  
  Purchase #6 $225.51   11.723%   $251.9465   $251.95   $251.95   $251.90  
  Purchase #7 $158.39   12.375%   $177.9908   $177.99   $178.00   $178.00  
  7 purchase totals = $1,023.46       $1,107.4651   $1,107.47   $1,107.45   $1,107.40