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	$247.77	11.174%	$275.4558	$275.46	$275.45	$275.50
Purchase #2	$56.72	4.642%	$59.3529	$59.35	$59.35	$59.40
Purchase #3	$232.37	13.440%	$263.6005	$263.60	$263.60	$263.60
Purchase #4	$96.55	12.452%	$108.5724	$108.57	$108.55	$108.60
Purchase #5	$207.65	10.850%	$230.18	$230.18	$230.20	$230.20
Purchase #6	$192.77	10.295%	$212.6157	$212.62	$212.60	$212.60
Purchase #7	$58.87	3.669%	$61.0299	$61.03	$61.05	$61.00
7 purchase totals =	$1,092.70		$1,210.8072	$1,210.81	$1,210.80	$1,210.90