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	$189.35	11.697%	$211.4983	$211.50	$211.50	$211.50
Purchase #2	$104.85	4.512%	$109.5808	$109.58	$109.60	$109.60
Purchase #3	$112.48	13.105%	$127.2205	$127.22	$127.20	$127.20
Purchase #4	$157.93	11.175%	$175.5787	$175.58	$175.60	$175.60
Purchase #5	$91.77	7.535%	$98.6849	$98.68	$98.70	$98.70
Purchase #6	$56.68	7.856%	$61.1328	$61.13	$61.15	$61.10
Purchase #7	$92.65	8.652%	$100.6661	$100.67	$100.65	$100.70
7 purchase totals =	$805.71		$884.3621	$884.36	$884.40	$884.40