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	$157.91	4.511%	$165.0333	$165.03	$165.05	$165.00
Purchase #2	$249.75	5.534%	$263.5712	$263.57	$263.55	$263.60
Purchase #3	$136.70	10.608%	$151.2011	$151.20	$151.20	$151.20
Purchase #4	$137.41	12.162%	$154.1218	$154.12	$154.10	$154.10
Purchase #5	$221.39	8.199%	$239.5418	$239.54	$239.55	$239.50
Purchase #6	$178.52	10.212%	$196.7505	$196.75	$196.75	$196.80
Purchase #7	$48.74	9.297%	$53.2714	$53.27	$53.25	$53.30
7 purchase totals =	$1,130.42		$1,223.4911	$1,223.48	$1,223.45	$1,223.50