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	$238.86	7.439%	$256.6288	$256.63	$256.65	$256.60
Purchase #2	$238.28	5.548%	$251.4998	$251.50	$251.50	$251.50
Purchase #3	$191.82	3.370%	$198.2843	$198.28	$198.30	$198.30
Purchase #4	$145.38	5.643%	$153.5838	$153.58	$153.60	$153.60
Purchase #5	$233.48	12.838%	$263.4542	$263.45	$263.45	$263.50
Purchase #6	$56.46	5.344%	$59.4772	$59.48	$59.50	$59.50
Purchase #7	$216.61	7.373%	$232.5807	$232.58	$232.60	$232.60
7 purchase totals =	$1,320.89		$1,415.5088	$1,415.50	$1,415.60	$1,415.60