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 $91.84   4.570%   $96.0371   $96.04   $96.05   $96.00  
  Purchase #2 $149.64   3.183%   $154.403   $154.40   $154.40   $154.40  
  Purchase #3 $11.62   8.787%   $12.641   $12.64   $12.65   $12.60  
  Purchase #4 $45.35   10.106%   $49.9331   $49.93   $49.95   $49.90  
  Purchase #5 $10.28   12.698%   $11.5854   $11.59   $11.60   $11.60  
  Purchase #6 $53.84   5.162%   $56.6192   $56.62   $56.60   $56.60  
  Purchase #7 $216.35   13.238%   $244.9904   $244.99   $245.00   $245.00  
  7 purchase totals = $578.92       $626.2092   $626.21   $626.25   $626.10