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 $84.92   13.458%   $96.3485   $96.35   $96.35   $96.30  
  Purchase #2 $198.25   7.184%   $212.4923   $212.49   $212.50   $212.50  
  Purchase #3 $219.67   9.115%   $239.6929   $239.69   $239.70   $239.70  
  Purchase #4 $133.64   11.456%   $148.9498   $148.95   $148.95   $148.90  
  Purchase #5 $129.61   5.299%   $136.478   $136.48   $136.50   $136.50  
  Purchase #6 $200.77   13.377%   $227.627   $227.63   $227.65   $227.60  
  Purchase #7 $94.66   6.628%   $100.9341   $100.93   $100.95   $100.90  
  7 purchase totals = $1,061.52       $1,162.5226   $1,162.52   $1,162.60   $1,162.40