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	$175.48	10.717%	$194.2862	$194.29	$194.30	$194.30
Purchase #2	$154.70	6.869%	$165.3263	$165.33	$165.35	$165.30
Purchase #3	$211.33	4.658%	$221.1738	$221.17	$221.15	$221.20
Purchase #4	$39.42	5.658%	$41.6504	$41.65	$41.65	$41.70
Purchase #5	$214.82	8.839%	$233.8079	$233.81	$233.80	$233.80
Purchase #6	$38.25	11.358%	$42.5944	$42.59	$42.60	$42.60
Purchase #7	$109.46	11.491%	$122.038	$122.04	$122.05	$122.00
7 purchase totals =	$943.46		$1,020.8770	$1,020.88	$1,020.90	$1,020.90