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	$165.47	6.179%	$175.6944	$175.69	$175.70	$175.70
Purchase #2	$47.39	9.773%	$52.0214	$52.02	$52.00	$52.00
Purchase #3	$41.92	7.487%	$45.0586	$45.06	$45.05	$45.10
Purchase #4	$132.82	5.343%	$139.9166	$139.92	$139.90	$139.90
Purchase #5	$105.73	11.625%	$118.0211	$118.02	$118.00	$118.00
Purchase #6	$44.37	5.411%	$46.7709	$46.77	$46.75	$46.80
Purchase #7	$195.25	13.795%	$222.1847	$222.18	$222.20	$222.20
7 purchase totals =	$732.95		$799.6677	$799.66	$799.60	$799.70