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	$213.32	9.425%	$233.4254	$233.43	$233.45	$233.40
Purchase #2	$70.67	10.345%	$77.9808	$77.98	$78.00	$78.00
Purchase #3	$118.80	4.847%	$124.5582	$124.56	$124.55	$124.60
Purchase #4	$89.37	12.158%	$100.2356	$100.24	$100.25	$100.20
Purchase #5	$233.99	12.451%	$263.1241	$263.12	$263.10	$263.10
Purchase #6	$244.89	3.282%	$252.9273	$252.93	$252.95	$252.90
Purchase #7	$173.63	13.258%	$196.6499	$196.65	$196.65	$196.60
7 purchase totals =	$1,144.67		$1,248.9013	$1,248.91	$1,248.95	$1,248.80