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	$76.56	7.317%	$82.1619	$82.16	$82.15	$82.20
Purchase #2	$11.92	3.373%	$12.3221	$12.32	$12.30	$12.30
Purchase #3	$53.77	7.461%	$57.7818	$57.78	$57.80	$57.80
Purchase #4	$144.78	10.122%	$159.4346	$159.43	$159.45	$159.40
Purchase #5	$85.86	4.330%	$89.5777	$89.58	$89.60	$89.60
Purchase #6	$158.46	8.718%	$172.2745	$172.27	$172.25	$172.30
Purchase #7	$231.75	5.213%	$243.8311	$243.83	$243.85	$243.80
7 purchase totals =	$763.10		$817.3837	$817.37	$817.40	$817.40