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	$35.91	7.140%	$38.474	$38.47	$38.45	$38.50
Purchase #2	$228.69	8.328%	$247.7353	$247.74	$247.75	$247.70
Purchase #3	$26.89	3.763%	$27.9019	$27.90	$27.90	$27.90
Purchase #4	$241.37	7.131%	$258.5821	$258.58	$258.60	$258.60
Purchase #5	$129.91	6.456%	$138.297	$138.30	$138.30	$138.30
Purchase #6	$76.30	12.286%	$85.6742	$85.67	$85.65	$85.70
Purchase #7	$81.35	11.103%	$90.3823	$90.38	$90.40	$90.40
7 purchase totals =	$820.42		$887.0468	$887.04	$887.05	$887.10