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	$104.25	11.103%	$115.8249	$115.82	$115.80	$115.80
Purchase #2	$61.46	6.286%	$65.3234	$65.32	$65.30	$65.30
Purchase #3	$162.28	7.158%	$173.896	$173.90	$173.90	$173.90
Purchase #4	$136.56	6.593%	$145.5634	$145.56	$145.55	$145.60
Purchase #5	$228.76	4.769%	$239.6696	$239.67	$239.65	$239.70
Purchase #6	$50.83	7.173%	$54.476	$54.48	$54.50	$54.50
Purchase #7	$46.80	11.482%	$52.1736	$52.17	$52.15	$52.20
7 purchase totals =	$790.94		$846.9269	$846.92	$846.85	$847.00