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	$10.59	3.643%	$10.9758	$10.98	$11.00	$11.00
Purchase #2	$230.66	10.265%	$254.3372	$254.34	$254.35	$254.30
Purchase #3	$195.47	12.223%	$219.3623	$219.36	$219.35	$219.40
Purchase #4	$140.69	3.144%	$145.1133	$145.11	$145.10	$145.10
Purchase #5	$54.26	8.214%	$58.7169	$58.72	$58.70	$58.70
Purchase #6	$84.52	6.406%	$89.9344	$89.93	$89.95	$89.90
Purchase #7	$78.28	13.672%	$88.9824	$88.98	$89.00	$89.00
7 purchase totals =	$794.47		$867.4223	$867.42	$867.45	$867.40