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	$102.48	11.743%	$114.5142	$114.51	$114.50	$114.50
Purchase #2	$29.92	9.411%	$32.7358	$32.74	$32.75	$32.70
Purchase #3	$149.27	13.658%	$169.6573	$169.66	$169.65	$169.70
Purchase #4	$205.89	9.575%	$225.604	$225.60	$225.60	$225.60
Purchase #5	$199.72	8.784%	$217.2634	$217.26	$217.25	$217.30
Purchase #6	$231.37	10.702%	$256.1312	$256.13	$256.15	$256.10
Purchase #7	$7.25	9.420%	$7.933	$7.93	$7.95	$7.90
7 purchase totals =	$925.90		$1,023.8389	$1,023.83	$1,023.85	$1,023.80