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	$35.74	13.800%	$40.6721	$40.67	$40.65	$40.70
Purchase #2	$245.42	4.390%	$256.1939	$256.19	$256.20	$256.20
Purchase #3	$60.37	6.778%	$64.4619	$64.46	$64.45	$64.50
Purchase #4	$41.77	11.580%	$46.607	$46.61	$46.60	$46.60
Purchase #5	$151.50	3.581%	$156.9252	$156.93	$156.95	$156.90
Purchase #6	$146.97	13.826%	$167.2901	$167.29	$167.30	$167.30
Purchase #7	$69.27	6.205%	$73.5682	$73.57	$73.55	$73.60
7 purchase totals =	$751.04		$805.7184	$805.72	$805.70	$805.80