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 $241.54   11.460%   $269.2205   $269.22   $269.20   $269.20  
  Purchase #2 $90.82   5.294%   $95.628   $95.63   $95.65   $95.60  
  Purchase #3 $44.37   9.297%   $48.4951   $48.50   $48.50   $48.50  
  Purchase #4 $132.60   9.293%   $144.9225   $144.92   $144.90   $144.90  
  Purchase #5 $72.71   3.260%   $75.0803   $75.08   $75.10   $75.10  
  Purchase #6 $170.82   11.266%   $190.0646   $190.06   $190.05   $190.10  
  Purchase #7 $215.76   3.686%   $223.7129   $223.71   $223.70   $223.70  
  7 purchase totals = $968.62       $1,047.1239   $1,047.12   $1,047.10   $1,047.10