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	$218.75	4.256%	$228.06	$228.06	$228.05	$228.10
Purchase #2	$66.93	10.437%	$73.9155	$73.92	$73.90	$73.90
Purchase #3	$104.88	13.626%	$119.1709	$119.17	$119.15	$119.20
Purchase #4	$147.78	4.624%	$154.6133	$154.61	$154.60	$154.60
Purchase #5	$126.88	13.688%	$144.2473	$144.25	$144.25	$144.20
Purchase #6	$18.72	10.128%	$20.616	$20.62	$20.60	$20.60
Purchase #7	$156.54	6.872%	$167.2974	$167.30	$167.30	$167.30
7 purchase totals =	$840.48		$907.9204	$907.93	$907.85	$907.90