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	$75.39	4.130%	$78.5036	$78.50	$78.50	$78.50
Purchase #2	$19.30	5.724%	$20.4047	$20.40	$20.40	$20.40
Purchase #3	$61.48	5.541%	$64.8866	$64.89	$64.90	$64.90
Purchase #4	$150.65	7.680%	$162.2199	$162.22	$162.20	$162.20
Purchase #5	$74.32	5.813%	$78.6402	$78.64	$78.65	$78.60
Purchase #6	$131.58	11.461%	$146.6604	$146.66	$146.65	$146.70
Purchase #7	$243.42	4.368%	$254.0526	$254.05	$254.05	$254.10
7 purchase totals =	$756.14		$805.3680	$805.36	$805.35	$805.40