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	$76.39	8.283%	$82.7174	$82.72	$82.70	$82.70
Purchase #2	$127.74	13.748%	$145.3017	$145.30	$145.30	$145.30
Purchase #3	$179.64	8.628%	$195.1393	$195.14	$195.15	$195.10
Purchase #4	$91.28	10.459%	$100.827	$100.83	$100.85	$100.80
Purchase #5	$37.78	5.621%	$39.9036	$39.90	$39.90	$39.90
Purchase #6	$136.83	4.792%	$143.3869	$143.39	$143.40	$143.40
Purchase #7	$61.45	8.347%	$66.5792	$66.58	$66.60	$66.60
7 purchase totals =	$711.11		$773.8551	$773.86	$773.90	$773.80