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 $213.61   5.841%   $226.087   $226.09   $226.10   $226.10  
  Purchase #2 $61.70   4.218%   $64.3025   $64.30   $64.30   $64.30  
  Purchase #3 $147.41   8.392%   $159.7806   $159.78   $159.80   $159.80  
  Purchase #4 $113.44   5.162%   $119.2958   $119.30   $119.30   $119.30  
  Purchase #5 $107.92   7.297%   $115.7949   $115.79   $115.80   $115.80  
  Purchase #6 $235.77   10.689%   $260.9715   $260.97   $260.95   $261.00  
  Purchase #7 $83.92   3.529%   $86.8815   $86.88   $86.90   $86.90  
  7 purchase totals = $963.77       $1,033.1138   $1,033.11   $1,033.15   $1,033.20