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	$186.86	6.611%	$199.2133	$199.21	$199.20	$199.20
Purchase #2	$136.30	11.312%	$151.7183	$151.72	$151.70	$151.70
Purchase #3	$156.86	9.694%	$172.066	$172.07	$172.05	$172.10
Purchase #4	$129.30	12.710%	$145.734	$145.73	$145.75	$145.70
Purchase #5	$223.46	11.693%	$249.5892	$249.59	$249.60	$249.60
Purchase #6	$48.29	5.107%	$50.7562	$50.76	$50.75	$50.80
Purchase #7	$93.45	7.271%	$100.2447	$100.24	$100.25	$100.20
7 purchase totals =	$974.52		$1,069.3217	$1,069.32	$1,069.30	$1,069.30