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	$150.31	3.669%	$155.8249	$155.82	$155.80	$155.80
Purchase #2	$142.42	7.204%	$152.6799	$152.68	$152.70	$152.70
Purchase #3	$12.78	5.707%	$13.5094	$13.51	$13.50	$13.50
Purchase #4	$98.37	13.531%	$111.6804	$111.68	$111.70	$111.70
Purchase #5	$171.97	9.361%	$188.0681	$188.07	$188.05	$188.10
Purchase #6	$165.73	8.292%	$179.4723	$179.47	$179.45	$179.50
Purchase #7	$73.62	13.177%	$83.3209	$83.32	$83.30	$83.30
7 purchase totals =	$815.20		$884.5559	$884.55	$884.50	$884.60