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	$41.86	6.141%	$44.4306	$44.43	$44.45	$44.40
Purchase #2	$170.55	4.739%	$178.6324	$178.63	$178.65	$178.60
Purchase #3	$118.36	13.325%	$134.1315	$134.13	$134.15	$134.10
Purchase #4	$211.58	5.369%	$222.9397	$222.94	$222.95	$222.90
Purchase #5	$162.29	6.818%	$173.3549	$173.35	$173.35	$173.40
Purchase #6	$240.54	12.795%	$271.3171	$271.32	$271.30	$271.30
Purchase #7	$106.36	5.154%	$111.8418	$111.84	$111.85	$111.80
7 purchase totals =	$1,051.54		$1,136.6480	$1,136.64	$1,136.70	$1,136.50