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	$185.87	12.391%	$208.9012	$208.90	$208.90	$208.90
Purchase #2	$205.49	4.443%	$214.6199	$214.62	$214.60	$214.60
Purchase #3	$55.71	6.827%	$59.5133	$59.51	$59.50	$59.50
Purchase #4	$226.39	11.528%	$252.4882	$252.49	$252.50	$252.50
Purchase #5	$82.66	8.522%	$89.7043	$89.70	$89.70	$89.70
Purchase #6	$119.93	11.534%	$133.7627	$133.76	$133.75	$133.80
Purchase #7	$95.54	4.632%	$99.9654	$99.97	$99.95	$100.00
7 purchase totals =	$971.59		$1,058.9550	$1,058.95	$1,058.90	$1,059.00