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	$190.33	12.816%	$214.7227	$214.72	$214.70	$214.70
Purchase #2	$25.62	9.621%	$28.0849	$28.08	$28.10	$28.10
Purchase #3	$102.50	5.486%	$108.1232	$108.12	$108.10	$108.10
Purchase #4	$83.53	13.816%	$95.0705	$95.07	$95.05	$95.10
Purchase #5	$32.54	7.768%	$35.0677	$35.07	$35.05	$35.10
Purchase #6	$102.97	6.425%	$109.5858	$109.59	$109.60	$109.60
Purchase #7	$142.73	5.680%	$150.8371	$150.84	$150.85	$150.80
7 purchase totals =	$680.22		$741.4919	$741.49	$741.45	$741.50