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	$153.80	13.343%	$174.3215	$174.32	$174.30	$174.30
Purchase #2	$140.74	4.676%	$147.321	$147.32	$147.30	$147.30
Purchase #3	$105.65	5.758%	$111.7333	$111.73	$111.75	$111.70
Purchase #4	$103.92	7.445%	$111.6568	$111.66	$111.65	$111.70
Purchase #5	$225.97	11.546%	$252.0605	$252.06	$252.05	$252.10
Purchase #6	$31.45	13.371%	$35.6552	$35.66	$35.65	$35.70
Purchase #7	$83.72	4.435%	$87.433	$87.43	$87.45	$87.40
7 purchase totals =	$845.25		$920.1813	$920.18	$920.15	$920.20