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	$111.28	3.574%	$115.2571	$115.26	$115.25	$115.30
Purchase #2	$143.94	5.321%	$151.599	$151.60	$151.60	$151.60
Purchase #3	$18.25	12.470%	$20.5258	$20.53	$20.55	$20.50
Purchase #4	$214.27	3.745%	$222.2944	$222.29	$222.30	$222.30
Purchase #5	$231.70	8.458%	$251.2972	$251.30	$251.30	$251.30
Purchase #6	$145.75	12.327%	$163.7166	$163.72	$163.70	$163.70
Purchase #7	$151.63	3.429%	$156.8294	$156.83	$156.85	$156.80
7 purchase totals =	$1,016.82		$1,081.5195	$1,081.53	$1,081.55	$1,081.50