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	$60.51	6.437%	$64.405	$64.41	$64.40	$64.40
Purchase #2	$40.63	12.236%	$45.6015	$45.60	$45.60	$45.60
Purchase #3	$16.41	9.711%	$18.0036	$18.00	$18.00	$18.00
Purchase #4	$89.77	11.740%	$100.309	$100.31	$100.30	$100.30
Purchase #5	$129.38	13.728%	$147.1413	$147.14	$147.15	$147.10
Purchase #6	$111.92	4.745%	$117.2306	$117.23	$117.25	$117.20
Purchase #7	$246.74	3.240%	$254.7344	$254.73	$254.75	$254.70
7 purchase totals =	$695.36		$747.4254	$747.42	$747.45	$747.30