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	$154.64	11.773%	$172.8458	$172.85	$172.85	$172.80
Purchase #2	$17.70	4.530%	$18.5018	$18.50	$18.50	$18.50
Purchase #3	$58.58	10.257%	$64.5886	$64.59	$64.60	$64.60
Purchase #4	$93.98	11.557%	$104.8413	$104.84	$104.85	$104.80
Purchase #5	$214.28	3.376%	$221.5141	$221.51	$221.50	$221.50
Purchase #6	$223.79	7.862%	$241.3844	$241.38	$241.40	$241.40
Purchase #7	$183.29	9.628%	$200.9372	$200.94	$200.95	$200.90
7 purchase totals =	$946.26		$1,024.6132	$1,024.61	$1,024.65	$1,024.50