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	$27.81	3.848%	$28.8801	$28.88	$28.90	$28.90
Purchase #2	$21.64	4.114%	$22.5303	$22.53	$22.55	$22.50
Purchase #3	$34.39	7.762%	$37.0594	$37.06	$37.05	$37.10
Purchase #4	$148.83	6.216%	$158.0813	$158.08	$158.10	$158.10
Purchase #5	$217.78	10.674%	$241.0258	$241.03	$241.05	$241.00
Purchase #6	$83.30	6.453%	$88.6753	$88.68	$88.70	$88.70
Purchase #7	$214.65	4.114%	$223.4807	$223.48	$223.50	$223.50
7 purchase totals =	$748.40		$799.7329	$799.74	$799.85	$799.80