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	$72.91	7.175%	$78.1413	$78.14	$78.15	$78.10
Purchase #2	$154.37	12.258%	$173.2927	$173.29	$173.30	$173.30
Purchase #3	$85.41	7.695%	$91.9823	$91.98	$92.00	$92.00
Purchase #4	$122.92	3.198%	$126.851	$126.85	$126.85	$126.90
Purchase #5	$11.57	13.146%	$13.091	$13.09	$13.10	$13.10
Purchase #6	$54.59	12.536%	$61.4334	$61.43	$61.45	$61.40
Purchase #7	$187.90	8.522%	$203.9128	$203.91	$203.90	$203.90
7 purchase totals =	$689.67		$748.7045	$748.69	$748.75	$748.70