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	$210.54	5.485%	$222.0881	$222.09	$222.10	$222.10
Purchase #2	$65.38	3.271%	$67.5186	$67.52	$67.50	$67.50
Purchase #3	$238.28	12.832%	$268.8561	$268.86	$268.85	$268.90
Purchase #4	$184.41	5.662%	$194.8513	$194.85	$194.85	$194.90
Purchase #5	$35.97	11.817%	$40.2206	$40.22	$40.20	$40.20
Purchase #6	$174.85	10.797%	$193.7286	$193.73	$193.75	$193.70
Purchase #7	$81.34	13.845%	$92.6015	$92.60	$92.60	$92.60
7 purchase totals =	$990.77		$1,079.8648	$1,079.87	$1,079.85	$1,079.90