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	$86.82	4.463%	$90.6948	$90.69	$90.70	$90.70
Purchase #2	$18.47	9.297%	$20.1872	$20.19	$20.20	$20.20
Purchase #3	$84.39	7.252%	$90.51	$90.51	$90.50	$90.50
Purchase #4	$164.34	3.513%	$170.1133	$170.11	$170.10	$170.10
Purchase #5	$34.25	5.864%	$36.2584	$36.26	$36.25	$36.30
Purchase #6	$148.95	7.846%	$160.6366	$160.64	$160.65	$160.60
Purchase #7	$139.34	11.715%	$155.6637	$155.66	$155.65	$155.70
7 purchase totals =	$676.56		$724.0640	$724.06	$724.05	$724.10