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 $162.85   11.857%   $182.1591   $182.16   $182.15   $182.20  
  Purchase #2 $121.71   10.653%   $134.6758   $134.68   $134.70   $134.70  
  Purchase #3 $186.52   5.670%   $197.0957   $197.10   $197.10   $197.10  
  Purchase #4 $207.86   6.716%   $221.8199   $221.82   $221.80   $221.80  
  Purchase #5 $174.26   4.640%   $182.3457   $182.35   $182.35   $182.30  
  Purchase #6 $63.50   6.223%   $67.4516   $67.45   $67.45   $67.50  
  Purchase #7 $25.99   11.129%   $28.8824   $28.88   $28.90   $28.90  
  7 purchase totals = $942.69       $1,014.4302   $1,014.44   $1,014.45   $1,014.50