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 $223.75   4.853%   $234.6086   $234.61   $234.60   $234.60  
  Purchase #2 $215.27   4.220%   $224.3544   $224.35   $224.35   $224.40  
  Purchase #3 $86.55   11.235%   $96.2739   $96.27   $96.25   $96.30  
  Purchase #4 $201.79   6.712%   $215.3341   $215.33   $215.35   $215.30  
  Purchase #5 $126.80   7.832%   $136.731   $136.73   $136.75   $136.70  
  Purchase #6 $30.84   8.236%   $33.38   $33.38   $33.40   $33.40  
  Purchase #7 $67.96   8.721%   $73.8868   $73.89   $73.90   $73.90  
  7 purchase totals = $952.96       $1,014.5688   $1,014.56   $1,014.60   $1,014.60