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 $233.28   3.659%   $241.8157   $241.82   $241.80   $241.80  
  Purchase #2 $24.41   8.748%   $26.5454   $26.55   $26.55   $26.50  
  Purchase #3 $178.74   4.523%   $186.8244   $186.82   $186.80   $186.80  
  Purchase #4 $87.71   4.871%   $91.9824   $91.98   $92.00   $92.00  
  Purchase #5 $206.57   12.241%   $231.8562   $231.86   $231.85   $231.90  
  Purchase #6 $221.72   5.563%   $234.0543   $234.05   $234.05   $234.10  
  Purchase #7 $9.95   12.107%   $11.1546   $11.15   $11.15   $11.20  
  7 purchase totals = $962.38       $1,024.2330   $1,024.23   $1,024.20   $1,024.30