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 $85.25   12.591%   $95.9838   $95.98   $96.00   $96.00  
  Purchase #2 $226.46   4.304%   $236.2068   $236.21   $236.20   $236.20  
  Purchase #3 $139.79   12.777%   $157.651   $157.65   $157.65   $157.70  
  Purchase #4 $70.78   3.660%   $73.3705   $73.37   $73.35   $73.40  
  Purchase #5 $212.31   10.325%   $234.231   $234.23   $234.25   $234.20  
  Purchase #6 $42.59   5.517%   $44.9397   $44.94   $44.95   $44.90  
  Purchase #7 $159.46   8.231%   $172.5852   $172.59   $172.60   $172.60  
  7 purchase totals = $936.64       $1,014.9680   $1,014.97   $1,015.00   $1,015.00