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	$191.72	9.103%	$209.1723	$209.17	$209.15	$209.20
Purchase #2	$144.76	5.746%	$153.0779	$153.08	$153.10	$153.10
Purchase #3	$97.80	13.770%	$111.2671	$111.27	$111.25	$111.30
Purchase #4	$23.52	5.588%	$24.8343	$24.83	$24.85	$24.80
Purchase #5	$87.66	4.474%	$91.5819	$91.58	$91.60	$91.60
Purchase #6	$239.37	10.375%	$264.2046	$264.20	$264.20	$264.20
Purchase #7	$187.35	6.754%	$200.0036	$200.00	$200.00	$200.00
7 purchase totals =	$972.18		$1,054.1417	$1,054.13	$1,054.15	$1,054.20