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	$92.86	6.593%	$98.9823	$98.98	$99.00	$99.00
Purchase #2	$239.65	6.793%	$255.9294	$255.93	$255.95	$255.90
Purchase #3	$163.80	13.388%	$185.7295	$185.73	$185.75	$185.70
Purchase #4	$143.59	6.819%	$153.3814	$153.38	$153.40	$153.40
Purchase #5	$44.26	6.120%	$46.9687	$46.97	$46.95	$47.00
Purchase #6	$56.28	9.862%	$61.8303	$61.83	$61.85	$61.80
Purchase #7	$186.95	12.397%	$210.1262	$210.13	$210.15	$210.10
7 purchase totals =	$927.39		$1,012.9478	$1,012.95	$1,013.05	$1,012.90