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 $72.62   5.587%   $76.6773   $76.68   $76.70   $76.70  
  Purchase #2 $14.77   10.758%   $16.359   $16.36   $16.35   $16.40  
  Purchase #3 $219.99   8.285%   $238.2162   $238.22   $238.20   $238.20  
  Purchase #4 $65.43   11.790%   $73.1442   $73.14   $73.15   $73.10  
  Purchase #5 $245.71   5.309%   $258.7547   $258.75   $258.75   $258.80  
  Purchase #6 $83.47   8.194%   $90.3095   $90.31   $90.30   $90.30  
  Purchase #7 $7.62   8.491%   $8.267   $8.27   $8.25   $8.30  
  7 purchase totals = $709.61       $761.7279   $761.73   $761.70   $761.80