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 $216.50   4.826%   $226.9483   $226.95   $226.95   $226.90  
  Purchase #2 $86.74   13.591%   $98.5288   $98.53   $98.55   $98.50  
  Purchase #3 $198.83   11.570%   $221.8346   $221.83   $221.85   $221.80  
  Purchase #4 $222.93   5.383%   $234.9303   $234.93   $234.95   $234.90  
  Purchase #5 $214.50   8.782%   $233.3374   $233.34   $233.35   $233.30  
  Purchase #6 $82.89   13.524%   $94.1   $94.10   $94.10   $94.10  
  Purchase #7 $44.72   3.129%   $46.1193   $46.12   $46.10   $46.10  
  7 purchase totals = $1,067.11       $1,155.7987   $1,155.80   $1,155.85   $1,155.60