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	$219.26	6.623%	$233.7816	$233.78	$233.80	$233.80
Purchase #2	$11.59	4.769%	$12.1427	$12.14	$12.15	$12.10
Purchase #3	$68.78	10.846%	$76.2399	$76.24	$76.25	$76.20
Purchase #4	$118.87	3.683%	$123.248	$123.25	$123.25	$123.20
Purchase #5	$9.56	13.778%	$10.8772	$10.88	$10.90	$10.90
Purchase #6	$122.59	3.786%	$127.2313	$127.23	$127.25	$127.20
Purchase #7	$90.53	5.609%	$95.6078	$95.61	$95.60	$95.60
7 purchase totals =	$641.18		$679.1285	$679.13	$679.20	$679.00