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	$189.32	5.156%	$199.0813	$199.08	$199.10	$199.10
Purchase #2	$16.27	13.247%	$18.4253	$18.43	$18.45	$18.40
Purchase #3	$51.88	9.661%	$56.8921	$56.89	$56.90	$56.90
Purchase #4	$99.83	11.268%	$111.0788	$111.08	$111.10	$111.10
Purchase #5	$53.37	8.394%	$57.8499	$57.85	$57.85	$57.80
Purchase #6	$48.36	10.410%	$53.3943	$53.39	$53.40	$53.40
Purchase #7	$100.97	4.463%	$105.4763	$105.48	$105.50	$105.50
7 purchase totals =	$560.00		$602.1980	$602.20	$602.30	$602.20