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	$167.41	7.499%	$179.9641	$179.96	$179.95	$180.00
Purchase #2	$126.43	6.225%	$134.3003	$134.30	$134.30	$134.30
Purchase #3	$37.61	8.695%	$40.8802	$40.88	$40.90	$40.90
Purchase #4	$189.75	13.233%	$214.8596	$214.86	$214.85	$214.90
Purchase #5	$48.82	9.235%	$53.3285	$53.33	$53.35	$53.30
Purchase #6	$19.57	3.471%	$20.2493	$20.25	$20.25	$20.20
Purchase #7	$145.32	8.428%	$157.5676	$157.57	$157.55	$157.60
7 purchase totals =	$734.91		$801.1496	$801.15	$801.15	$801.20