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	$36.92	3.501%	$38.2126	$38.21	$38.20	$38.20
Purchase #2	$233.33	13.445%	$264.7012	$264.70	$264.70	$264.70
Purchase #3	$239.29	12.460%	$269.1055	$269.11	$269.10	$269.10
Purchase #4	$145.82	4.533%	$152.43	$152.43	$152.45	$152.40
Purchase #5	$167.94	8.203%	$181.7161	$181.72	$181.70	$181.70
Purchase #6	$189.43	13.104%	$214.2529	$214.25	$214.25	$214.30
Purchase #7	$72.61	4.174%	$75.6407	$75.64	$75.65	$75.60
7 purchase totals =	$1,085.34		$1,196.0590	$1,196.06	$1,196.05	$1,196.00