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	$146.26	8.410%	$158.5605	$158.56	$158.55	$158.60
Purchase #2	$168.42	7.660%	$181.321	$181.32	$181.30	$181.30
Purchase #3	$64.68	10.118%	$71.2243	$71.22	$71.20	$71.20
Purchase #4	$64.92	7.388%	$69.7163	$69.72	$69.70	$69.70
Purchase #5	$73.75	7.303%	$79.136	$79.14	$79.15	$79.10
Purchase #6	$80.54	11.187%	$89.55	$89.55	$89.55	$89.60
Purchase #7	$80.60	3.451%	$83.3815	$83.38	$83.40	$83.40
7 purchase totals =	$679.17		$732.8896	$732.89	$732.85	$732.90