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 $236.36   11.621%   $263.8274   $263.83   $263.85   $263.80  
  Purchase #2 $226.37   9.289%   $247.3975   $247.40   $247.40   $247.40  
  Purchase #3 $83.94   9.539%   $91.947   $91.95   $91.95   $91.90  
  Purchase #4 $190.83   8.678%   $207.3902   $207.39   $207.40   $207.40  
  Purchase #5 $44.42   3.606%   $46.0218   $46.02   $46.00   $46.00  
  Purchase #6 $94.79   4.343%   $98.9067   $98.91   $98.90   $98.90  
  Purchase #7 $134.78   4.124%   $140.3383   $140.34   $140.35   $140.30  
  7 purchase totals = $1,011.49       $1,095.8289   $1,095.84   $1,095.85   $1,095.70