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	$91.85	10.363%	$101.3684	$101.37	$101.35	$101.40
Purchase #2	$45.40	10.696%	$50.256	$50.26	$50.25	$50.30
Purchase #3	$86.43	4.769%	$90.5518	$90.55	$90.55	$90.60
Purchase #4	$234.29	10.707%	$259.3754	$259.38	$259.40	$259.40
Purchase #5	$66.45	3.215%	$68.5864	$68.59	$68.60	$68.60
Purchase #6	$88.56	4.239%	$92.3141	$92.31	$92.30	$92.30
Purchase #7	$127.78	12.260%	$143.4458	$143.45	$143.45	$143.40
7 purchase totals =	$740.76		$805.8979	$805.91	$805.90	$806.00