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 $174.99   12.367%   $196.631   $196.63   $196.65   $196.60  
  Purchase #2 $211.30   10.775%   $234.0676   $234.07   $234.05   $234.10  
  Purchase #3 $16.55   7.344%   $17.7654   $17.77   $17.75   $17.80  
  Purchase #4 $119.29   13.335%   $135.1973   $135.20   $135.20   $135.20  
  Purchase #5 $209.78   4.153%   $218.4922   $218.49   $218.50   $218.50  
  Purchase #6 $148.44   9.818%   $163.0138   $163.01   $163.00   $163.00  
  Purchase #7 $92.41   3.276%   $95.4374   $95.44   $95.45   $95.40  
  7 purchase totals = $972.76       $1,060.6047   $1,060.61   $1,060.60   $1,060.60