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	$71.75	6.262%	$76.243	$76.24	$76.25	$76.20
Purchase #2	$118.89	8.415%	$128.8946	$128.89	$128.90	$128.90
Purchase #3	$94.28	6.780%	$100.6722	$100.67	$100.65	$100.70
Purchase #4	$228.68	9.864%	$251.237	$251.24	$251.25	$251.20
Purchase #5	$199.89	10.189%	$220.2568	$220.26	$220.25	$220.30
Purchase #6	$145.96	13.401%	$165.5201	$165.52	$165.50	$165.50
Purchase #7	$42.55	10.278%	$46.9233	$46.92	$46.90	$46.90
7 purchase totals =	$902.00		$989.7470	$989.74	$989.70	$989.70