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	$185.62	12.476%	$208.778	$208.78	$208.80	$208.80
Purchase #2	$43.88	4.795%	$45.984	$45.98	$46.00	$46.00
Purchase #3	$114.75	6.549%	$122.265	$122.27	$122.25	$122.30
Purchase #4	$117.77	8.615%	$127.9159	$127.92	$127.90	$127.90
Purchase #5	$216.93	13.150%	$245.4563	$245.46	$245.45	$245.50
Purchase #6	$205.43	4.248%	$214.1567	$214.16	$214.15	$214.20
Purchase #7	$118.98	4.491%	$124.3234	$124.32	$124.30	$124.30
7 purchase totals =	$1,003.36		$1,088.8793	$1,088.89	$1,088.85	$1,089.00