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 $89.27   5.253%   $93.9594   $93.96   $93.95   $94.00  
  Purchase #2 $229.69   4.867%   $240.869   $240.87   $240.85   $240.90  
  Purchase #3 $52.47   10.173%   $57.8078   $57.81   $57.80   $57.80  
  Purchase #4 $125.67   4.238%   $130.9959   $131.00   $131.00   $131.00  
  Purchase #5 $236.79   11.393%   $263.7675   $263.77   $263.75   $263.80  
  Purchase #6 $242.70   13.861%   $276.3406   $276.34   $276.35   $276.30  
  Purchase #7 $39.75   7.657%   $42.7937   $42.79   $42.80   $42.80  
  7 purchase totals = $1,016.34       $1,106.5339   $1,106.54   $1,106.50   $1,106.60