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 $46.56   5.127%   $48.9471   $48.95   $48.95   $48.90  
  Purchase #2 $25.99   12.227%   $29.1678   $29.17   $29.15   $29.20  
  Purchase #3 $145.94   3.514%   $151.0683   $151.07   $151.05   $151.10  
  Purchase #4 $176.49   8.795%   $192.0123   $192.01   $192.00   $192.00  
  Purchase #5 $35.57   8.617%   $38.6351   $38.64   $38.65   $38.60  
  Purchase #6 $86.92   6.698%   $92.7419   $92.74   $92.75   $92.70  
  Purchase #7 $229.95   8.146%   $248.6817   $248.68   $248.70   $248.70  
  7 purchase totals = $747.42       $801.2542   $801.26   $801.25   $801.20