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	$156.98	5.760%	$166.022	$166.02	$166.00	$166.00
Purchase #2	$105.83	5.450%	$111.5977	$111.60	$111.60	$111.60
Purchase #3	$143.56	12.696%	$161.7864	$161.79	$161.80	$161.80
Purchase #4	$169.89	8.200%	$183.821	$183.82	$183.80	$183.80
Purchase #5	$89.92	6.533%	$95.7945	$95.79	$95.80	$95.80
Purchase #6	$163.85	6.743%	$174.8984	$174.90	$174.90	$174.90
Purchase #7	$154.49	11.655%	$172.4958	$172.50	$172.50	$172.50
7 purchase totals =	$984.52		$1,066.4158	$1,066.42	$1,066.40	$1,066.40