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	$26.30	12.568%	$29.6054	$29.61	$29.60	$29.60
Purchase #2	$184.97	6.371%	$196.7544	$196.75	$196.75	$196.80
Purchase #3	$53.47	10.806%	$59.248	$59.25	$59.25	$59.20
Purchase #4	$30.28	4.388%	$31.6087	$31.61	$31.60	$31.60
Purchase #5	$31.37	10.712%	$34.7304	$34.73	$34.75	$34.70
Purchase #6	$15.91	7.352%	$17.0797	$17.08	$17.10	$17.10
Purchase #7	$122.78	3.517%	$127.0982	$127.10	$127.10	$127.10
7 purchase totals =	$465.08		$496.1248	$496.13	$496.15	$496.10