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	$161.47	8.734%	$175.5728	$175.57	$175.55	$175.60
Purchase #2	$101.50	10.842%	$112.5046	$112.50	$112.50	$112.50
Purchase #3	$40.28	3.140%	$41.5448	$41.54	$41.55	$41.50
Purchase #4	$20.89	9.865%	$22.9508	$22.95	$22.95	$23.00
Purchase #5	$86.81	5.379%	$91.4795	$91.48	$91.50	$91.50
Purchase #6	$121.91	13.705%	$138.6178	$138.62	$138.60	$138.60
Purchase #7	$121.56	5.169%	$127.8434	$127.84	$127.85	$127.80
7 purchase totals =	$654.42		$710.5137	$710.50	$710.50	$710.50