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 $201.48   5.170%   $211.8965   $211.90   $211.90   $211.90  
  Purchase #2 $15.75   8.255%   $17.0502   $17.05   $17.05   $17.10  
  Purchase #3 $171.33   5.699%   $181.0941   $181.09   $181.10   $181.10  
  Purchase #4 $100.97   9.578%   $110.6409   $110.64   $110.65   $110.60  
  Purchase #5 $64.37   10.539%   $71.154   $71.15   $71.15   $71.20  
  Purchase #6 $32.62   3.154%   $33.6488   $33.65   $33.65   $33.60  
  Purchase #7 $130.28   5.120%   $136.9503   $136.95   $136.95   $137.00  
  7 purchase totals = $716.80       $762.4348   $762.43   $762.45   $762.50