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	$49.84	4.618%	$52.1416	$52.14	$52.15	$52.10
Purchase #2	$74.77	3.700%	$77.5365	$77.54	$77.55	$77.50
Purchase #3	$118.29	7.431%	$127.0801	$127.08	$127.10	$127.10
Purchase #4	$18.64	10.408%	$20.5801	$20.58	$20.60	$20.60
Purchase #5	$148.62	5.825%	$157.2771	$157.28	$157.30	$157.30
Purchase #6	$195.79	7.468%	$210.4116	$210.41	$210.40	$210.40
Purchase #7	$157.30	4.554%	$164.4634	$164.46	$164.45	$164.50
7 purchase totals =	$763.25		$809.4904	$809.49	$809.55	$809.50