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	$148.94	6.291%	$158.3098	$158.31	$158.30	$158.30
Purchase #2	$61.72	7.532%	$66.3688	$66.37	$66.35	$66.40
Purchase #3	$163.43	4.505%	$170.7925	$170.79	$170.80	$170.80
Purchase #4	$159.95	4.361%	$166.9254	$166.93	$166.95	$166.90
Purchase #5	$104.92	8.107%	$113.4259	$113.43	$113.45	$113.40
Purchase #6	$210.41	5.850%	$222.719	$222.72	$222.70	$222.70
Purchase #7	$225.64	3.583%	$233.7247	$233.72	$233.70	$233.70
7 purchase totals =	$1,075.01		$1,132.2661	$1,132.27	$1,132.25	$1,132.20