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	$167.83	10.687%	$185.766	$185.77	$185.75	$185.80
Purchase #2	$190.69	7.739%	$205.4475	$205.45	$205.45	$205.40
Purchase #3	$245.52	5.633%	$259.3501	$259.35	$259.35	$259.40
Purchase #4	$60.61	11.681%	$67.6899	$67.69	$67.70	$67.70
Purchase #5	$211.51	8.758%	$230.034	$230.03	$230.05	$230.00
Purchase #6	$231.84	4.604%	$242.5139	$242.51	$242.50	$242.50
Purchase #7	$147.57	3.229%	$152.335	$152.34	$152.35	$152.30
7 purchase totals =	$1,255.57		$1,343.1364	$1,343.14	$1,343.15	$1,343.10