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	$128.72	11.536%	$143.5691	$143.57	$143.55	$143.60
Purchase #2	$109.99	3.577%	$113.9243	$113.92	$113.90	$113.90
Purchase #3	$229.38	6.618%	$244.5604	$244.56	$244.55	$244.60
Purchase #4	$136.28	9.291%	$148.9418	$148.94	$148.95	$148.90
Purchase #5	$130.29	12.219%	$146.2101	$146.21	$146.20	$146.20
Purchase #6	$129.91	10.419%	$143.4453	$143.45	$143.45	$143.40
Purchase #7	$63.30	5.242%	$66.6182	$66.62	$66.60	$66.60
7 purchase totals =	$927.87		$1,007.2692	$1,007.27	$1,007.20	$1,007.20