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	$89.31	12.419%	$100.4014	$100.40	$100.40	$100.40
Purchase #2	$31.27	10.648%	$34.5996	$34.60	$34.60	$34.60
Purchase #3	$57.51	4.358%	$60.0163	$60.02	$60.00	$60.00
Purchase #4	$235.38	8.142%	$254.5446	$254.54	$254.55	$254.50
Purchase #5	$214.50	3.446%	$221.8917	$221.89	$221.90	$221.90
Purchase #6	$231.54	5.388%	$244.0154	$244.02	$244.00	$244.00
Purchase #7	$16.42	8.375%	$17.7952	$17.80	$17.80	$17.80
7 purchase totals =	$875.93		$933.2642	$933.27	$933.25	$933.20