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	$48.82	4.485%	$51.0096	$51.01	$51.00	$51.00
Purchase #2	$8.76	5.567%	$9.2477	$9.25	$9.25	$9.20
Purchase #3	$241.91	5.635%	$255.5416	$255.54	$255.55	$255.50
Purchase #4	$102.32	13.804%	$116.4443	$116.44	$116.45	$116.40
Purchase #5	$30.75	5.285%	$32.3751	$32.38	$32.40	$32.40
Purchase #6	$33.54	10.669%	$37.1184	$37.12	$37.10	$37.10
Purchase #7	$172.91	13.425%	$196.1232	$196.12	$196.10	$196.10
7 purchase totals =	$639.01		$697.8599	$697.86	$697.85	$697.70