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	$173.92	3.705%	$180.3637	$180.36	$180.35	$180.40
Purchase #2	$26.70	10.849%	$29.5967	$29.60	$29.60	$29.60
Purchase #3	$196.29	9.250%	$214.4468	$214.45	$214.45	$214.40
Purchase #4	$213.34	7.707%	$229.7821	$229.78	$229.80	$229.80
Purchase #5	$223.97	4.397%	$233.818	$233.82	$233.80	$233.80
Purchase #6	$105.25	8.603%	$114.3047	$114.30	$114.30	$114.30
Purchase #7	$130.40	10.302%	$143.8338	$143.83	$143.85	$143.80
7 purchase totals =	$1,069.87		$1,146.1458	$1,146.14	$1,146.15	$1,146.10