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	$196.57	3.870%	$204.1773	$204.18	$204.20	$204.20
Purchase #2	$223.72	13.487%	$253.8931	$253.89	$253.90	$253.90
Purchase #3	$82.89	4.463%	$86.5894	$86.59	$86.60	$86.60
Purchase #4	$116.52	9.794%	$127.932	$127.93	$127.95	$127.90
Purchase #5	$129.48	5.209%	$136.2246	$136.22	$136.20	$136.20
Purchase #6	$232.74	8.254%	$251.9504	$251.95	$251.95	$252.00
Purchase #7	$89.27	6.772%	$95.3154	$95.32	$95.30	$95.30
7 purchase totals =	$1,071.19		$1,156.0822	$1,156.08	$1,156.10	$1,156.10