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	$57.71	11.406%	$64.2924	$64.29	$64.30	$64.30
Purchase #2	$141.81	11.142%	$157.6105	$157.61	$157.60	$157.60
Purchase #3	$89.51	12.721%	$100.8966	$100.90	$100.90	$100.90
Purchase #4	$79.39	11.423%	$88.4587	$88.46	$88.45	$88.50
Purchase #5	$172.26	10.162%	$189.7651	$189.77	$189.75	$189.80
Purchase #6	$199.88	7.304%	$214.4792	$214.48	$214.50	$214.50
Purchase #7	$248.90	12.417%	$279.8059	$279.81	$279.80	$279.80
7 purchase totals =	$989.46		$1,095.3084	$1,095.32	$1,095.30	$1,095.40