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 $186.71   10.650%   $206.5946   $206.59   $206.60   $206.60  
  Purchase #2 $127.97   4.756%   $134.0563   $134.06   $134.05   $134.10  
  Purchase #3 $190.94   9.251%   $208.6039   $208.60   $208.60   $208.60  
  Purchase #4 $46.56   5.829%   $49.274   $49.27   $49.25   $49.30  
  Purchase #5 $192.97   5.227%   $203.0565   $203.06   $203.05   $203.10  
  Purchase #6 $204.90   6.627%   $218.4787   $218.48   $218.50   $218.50  
  Purchase #7 $87.98   4.326%   $91.786   $91.79   $91.80   $91.80  
  7 purchase totals = $1,038.03       $1,111.8500   $1,111.85   $1,111.85   $1,112.00