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	$154.58	12.320%	$173.6243	$173.62	$173.60	$173.60
Purchase #2	$248.72	13.254%	$281.6853	$281.69	$281.70	$281.70
Purchase #3	$19.89	7.859%	$21.4532	$21.45	$21.45	$21.50
Purchase #4	$94.30	11.508%	$105.152	$105.15	$105.15	$105.20
Purchase #5	$48.43	8.534%	$52.563	$52.56	$52.55	$52.60
Purchase #6	$202.87	4.253%	$211.4981	$211.50	$211.50	$211.50
Purchase #7	$237.95	6.867%	$254.29	$254.29	$254.30	$254.30
7 purchase totals =	$1,006.74		$1,100.2659	$1,100.26	$1,100.25	$1,100.40