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 $214.43   5.410%   $226.0307   $226.03   $226.05   $226.00  
  Purchase #2 $95.92   6.215%   $101.8814   $101.88   $101.90   $101.90  
  Purchase #3 $81.95   13.342%   $92.8838   $92.88   $92.90   $92.90  
  Purchase #4 $118.76   13.501%   $134.7938   $134.79   $134.80   $134.80  
  Purchase #5 $48.72   5.364%   $51.3333   $51.33   $51.35   $51.30  
  Purchase #6 $199.35   7.125%   $213.5537   $213.55   $213.55   $213.60  
  Purchase #7 $118.50   11.796%   $132.4783   $132.48   $132.50   $132.50  
  7 purchase totals = $877.63       $952.9550   $952.94   $953.05   $953.00