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	$57.49	11.585%	$64.1502	$64.15	$64.15	$64.20
Purchase #2	$41.72	4.716%	$43.6875	$43.69	$43.70	$43.70
Purchase #3	$247.30	3.182%	$255.1691	$255.17	$255.15	$255.20
Purchase #4	$147.56	3.580%	$152.8426	$152.84	$152.85	$152.80
Purchase #5	$82.32	12.518%	$92.6248	$92.62	$92.60	$92.60
Purchase #6	$101.74	10.369%	$112.2894	$112.29	$112.30	$112.30
Purchase #7	$156.54	7.741%	$168.6578	$168.66	$168.65	$168.70
7 purchase totals =	$834.67		$889.4214	$889.42	$889.40	$889.50