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	$219.59	11.342%	$244.4959	$244.50	$244.50	$244.50
Purchase #2	$89.58	3.201%	$92.4475	$92.45	$92.45	$92.40
Purchase #3	$44.61	4.628%	$46.6746	$46.67	$46.65	$46.70
Purchase #4	$34.92	10.160%	$38.4679	$38.47	$38.45	$38.50
Purchase #5	$172.97	8.629%	$187.8956	$187.90	$187.90	$187.90
Purchase #6	$114.98	10.702%	$127.2852	$127.29	$127.30	$127.30
Purchase #7	$224.73	6.527%	$239.3981	$239.40	$239.40	$239.40
7 purchase totals =	$901.38		$976.6648	$976.68	$976.65	$976.70