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 $144.80   4.699%   $151.6042   $151.60   $151.60   $151.60  
  Purchase #2 $215.80   13.691%   $245.3452   $245.35   $245.35   $245.30  
  Purchase #3 $69.25   9.826%   $76.0545   $76.05   $76.05   $76.10  
  Purchase #4 $137.72   4.304%   $143.6475   $143.65   $143.65   $143.60  
  Purchase #5 $197.45   4.386%   $206.1102   $206.11   $206.10   $206.10  
  Purchase #6 $103.25   6.204%   $109.6556   $109.66   $109.65   $109.70  
  Purchase #7 $122.28   6.805%   $130.6012   $130.60   $130.60   $130.60  
  7 purchase totals = $990.55       $1,063.0184   $1,063.02   $1,063.00   $1,063.00