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	$197.56	3.729%	$204.927	$204.93	$204.95	$204.90
Purchase #2	$210.30	10.803%	$233.0187	$233.02	$233.00	$233.00
Purchase #3	$142.43	6.323%	$151.4358	$151.44	$151.45	$151.40
Purchase #4	$128.44	13.521%	$145.8064	$145.81	$145.80	$145.80
Purchase #5	$230.48	10.190%	$253.9659	$253.97	$253.95	$254.00
Purchase #6	$111.68	13.139%	$126.3536	$126.35	$126.35	$126.40
Purchase #7	$88.71	12.853%	$100.1119	$100.11	$100.10	$100.10
7 purchase totals =	$1,109.60		$1,215.6193	$1,215.63	$1,215.60	$1,215.60