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 $220.49   5.522%   $232.6655   $232.67   $232.65   $232.70  
  Purchase #2 $118.78   3.351%   $122.7603   $122.76   $122.75   $122.80  
  Purchase #3 $193.99   6.363%   $206.3336   $206.33   $206.35   $206.30  
  Purchase #4 $96.35   10.649%   $106.6103   $106.61   $106.60   $106.60  
  Purchase #5 $96.99   7.125%   $103.9005   $103.90   $103.90   $103.90  
  Purchase #6 $33.78   3.806%   $35.0657   $35.07   $35.05   $35.10  
  Purchase #7 $234.70   11.460%   $261.5966   $261.60   $261.60   $261.60  
  7 purchase totals = $995.08       $1,068.9325   $1,068.94   $1,068.90   $1,069.00