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 $46.80   5.772%   $49.5013   $49.50   $49.50   $49.50  
  Purchase #2 $91.39   12.705%   $103.0011   $103.00   $103.00   $103.00  
  Purchase #3 $23.84   10.538%   $26.3523   $26.35   $26.35   $26.40  
  Purchase #4 $195.43   5.707%   $206.5832   $206.58   $206.60   $206.60  
  Purchase #5 $151.58   6.283%   $161.1038   $161.10   $161.10   $161.10  
  Purchase #6 $199.46   3.202%   $205.8467   $205.85   $205.85   $205.80  
  Purchase #7 $187.74   10.788%   $207.9934   $207.99   $208.00   $208.00  
  7 purchase totals = $896.24       $960.3818   $960.37   $960.40   $960.40