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 $83.76   13.427%   $95.0065   $95.01   $95.00   $95.00  
  Purchase #2 $10.78   7.438%   $11.5818   $11.58   $11.60   $11.60  
  Purchase #3 $132.42   10.366%   $146.1467   $146.15   $146.15   $146.10  
  Purchase #4 $28.85   5.463%   $30.4261   $30.43   $30.45   $30.40  
  Purchase #5 $219.81   9.795%   $241.3404   $241.34   $241.35   $241.30  
  Purchase #6 $225.36   7.786%   $242.9065   $242.91   $242.90   $242.90  
  Purchase #7 $65.97   3.318%   $68.1589   $68.16   $68.15   $68.20  
  7 purchase totals = $766.95       $835.5669   $835.58   $835.60   $835.50