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	$104.90	13.325%	$118.8779	$118.88	$118.90	$118.90
Purchase #2	$74.61	5.158%	$78.4584	$78.46	$78.45	$78.50
Purchase #3	$145.44	4.778%	$152.3891	$152.39	$152.40	$152.40
Purchase #4	$184.58	8.368%	$200.0257	$200.03	$200.05	$200.00
Purchase #5	$50.88	7.805%	$54.8512	$54.85	$54.85	$54.90
Purchase #6	$50.77	3.644%	$52.6201	$52.62	$52.60	$52.60
Purchase #7	$191.41	3.374%	$197.8682	$197.87	$197.85	$197.90
7 purchase totals =	$802.59		$855.0906	$855.10	$855.10	$855.20