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	$50.42	11.241%	$56.0877	$56.09	$56.10	$56.10
Purchase #2	$182.81	9.411%	$200.0142	$200.01	$200.00	$200.00
Purchase #3	$235.56	4.689%	$246.6054	$246.61	$246.60	$246.60
Purchase #4	$228.86	4.655%	$239.5134	$239.51	$239.50	$239.50
Purchase #5	$72.37	7.860%	$78.0583	$78.06	$78.05	$78.10
Purchase #6	$23.91	7.408%	$25.6813	$25.68	$25.70	$25.70
Purchase #7	$158.45	7.378%	$170.1404	$170.14	$170.15	$170.10
7 purchase totals =	$952.38		$1,016.1007	$1,016.10	$1,016.10	$1,016.10