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	$151.98	6.832%	$162.3633	$162.36	$162.35	$162.40
Purchase #2	$107.79	8.213%	$116.6428	$116.64	$116.65	$116.60
Purchase #3	$95.88	4.828%	$100.5091	$100.51	$100.50	$100.50
Purchase #4	$241.57	4.374%	$252.1363	$252.14	$252.15	$252.10
Purchase #5	$121.40	13.546%	$137.8448	$137.84	$137.85	$137.80
Purchase #6	$167.41	10.222%	$184.5227	$184.52	$184.50	$184.50
Purchase #7	$200.58	5.473%	$211.5577	$211.56	$211.55	$211.60
7 purchase totals =	$1,086.61		$1,165.5767	$1,165.57	$1,165.55	$1,165.50