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	$161.65	12.552%	$181.9403	$181.94	$181.95	$181.90
Purchase #2	$146.69	8.138%	$158.6276	$158.63	$158.65	$158.60
Purchase #3	$234.85	8.415%	$254.6126	$254.61	$254.60	$254.60
Purchase #4	$75.93	7.351%	$81.5116	$81.51	$81.50	$81.50
Purchase #5	$79.28	13.152%	$89.7069	$89.71	$89.70	$89.70
Purchase #6	$179.69	7.138%	$192.5163	$192.52	$192.50	$192.50
Purchase #7	$152.84	13.198%	$173.0118	$173.01	$173.00	$173.00
7 purchase totals =	$1,030.93		$1,131.9271	$1,131.93	$1,131.90	$1,131.80