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 $92.39   12.148%   $103.6135   $103.61   $103.60   $103.60  
  Purchase #2 $11.50   10.724%   $12.7333   $12.73   $12.75   $12.70  
  Purchase #3 $235.59   11.315%   $262.247   $262.25   $262.25   $262.20  
  Purchase #4 $14.99   7.500%   $16.1143   $16.11   $16.10   $16.10  
  Purchase #5 $168.30   10.451%   $185.889   $185.89   $185.90   $185.90  
  Purchase #6 $182.95   6.427%   $194.7082   $194.71   $194.70   $194.70  
  Purchase #7 $232.99   3.716%   $241.6479   $241.65   $241.65   $241.60  
  7 purchase totals = $938.71       $1,016.9532   $1,016.95   $1,016.95   $1,016.80