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	$238.77	11.734%	$266.7873	$266.79	$266.80	$266.80
Purchase #2	$125.63	4.707%	$131.5434	$131.54	$131.55	$131.50
Purchase #3	$188.50	11.533%	$210.2397	$210.24	$210.25	$210.20
Purchase #4	$86.97	9.294%	$95.053	$95.05	$95.05	$95.10
Purchase #5	$103.43	10.279%	$114.0616	$114.06	$114.05	$114.10
Purchase #6	$104.83	8.178%	$113.403	$113.40	$113.40	$113.40
Purchase #7	$105.31	5.540%	$111.1442	$111.14	$111.15	$111.10
7 purchase totals =	$953.44		$1,042.2322	$1,042.22	$1,042.25	$1,042.20