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 $217.47   11.603%   $242.703   $242.70   $242.70   $242.70  
  Purchase #2 $226.25   11.154%   $251.4859   $251.49   $251.50   $251.50  
  Purchase #3 $200.48   8.732%   $217.9859   $217.99   $218.00   $218.00  
  Purchase #4 $184.55   11.630%   $206.0132   $206.01   $206.00   $206.00  
  Purchase #5 $220.40   3.235%   $227.5299   $227.53   $227.55   $227.50  
  Purchase #6 $53.28   4.446%   $55.6488   $55.65   $55.65   $55.60  
  Purchase #7 $250.52   9.304%   $273.8284   $273.83   $273.85   $273.80  
  7 purchase totals = $1,352.95       $1,475.1951   $1,475.20   $1,475.25   $1,475.10