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	$90.82	4.205%	$94.639	$94.64	$94.65	$94.60
Purchase #2	$43.37	4.319%	$45.2432	$45.24	$45.25	$45.20
Purchase #3	$41.69	4.717%	$43.6565	$43.66	$43.65	$43.70
Purchase #4	$221.68	5.318%	$233.4689	$233.47	$233.45	$233.50
Purchase #5	$60.50	12.475%	$68.0474	$68.05	$68.05	$68.00
Purchase #6	$64.30	5.583%	$67.8899	$67.89	$67.90	$67.90
Purchase #7	$77.93	13.460%	$88.4194	$88.42	$88.40	$88.40
7 purchase totals =	$600.29		$641.3643	$641.37	$641.35	$641.30