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 $62.29   11.729%   $69.596   $69.60   $69.60   $69.60  
  Purchase #2 $168.56   5.469%   $177.7785   $177.78   $177.80   $177.80  
  Purchase #3 $217.60   4.444%   $227.2701   $227.27   $227.25   $227.30  
  Purchase #4 $29.75   3.548%   $30.8055   $30.81   $30.80   $30.80  
  Purchase #5 $47.63   6.349%   $50.654   $50.65   $50.65   $50.70  
  Purchase #6 $76.59   10.722%   $84.802   $84.80   $84.80   $84.80  
  Purchase #7 $223.83   9.852%   $245.8817   $245.88   $245.90   $245.90  
  7 purchase totals = $826.25       $886.7878   $886.79   $886.80   $886.90