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	$248.40	6.219%	$263.848	$263.85	$263.85	$263.80
Purchase #2	$250.51	10.873%	$277.748	$277.75	$277.75	$277.70
Purchase #3	$13.72	13.596%	$15.5854	$15.59	$15.60	$15.60
Purchase #4	$111.93	10.654%	$123.855	$123.86	$123.85	$123.90
Purchase #5	$86.70	7.111%	$92.8652	$92.87	$92.85	$92.90
Purchase #6	$211.77	4.546%	$221.3971	$221.40	$221.40	$221.40
Purchase #7	$249.28	3.427%	$257.8228	$257.82	$257.80	$257.80
7 purchase totals =	$1,172.31		$1,253.1215	$1,253.14	$1,253.10	$1,253.10