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	$158.72	9.402%	$173.6429	$173.64	$173.65	$173.60
Purchase #2	$19.93	6.148%	$21.1553	$21.16	$21.15	$21.20
Purchase #3	$52.62	4.219%	$54.84	$54.84	$54.85	$54.80
Purchase #4	$223.83	7.764%	$241.2082	$241.21	$241.20	$241.20
Purchase #5	$72.72	13.818%	$82.7684	$82.77	$82.75	$82.80
Purchase #6	$183.27	3.832%	$190.2929	$190.29	$190.30	$190.30
Purchase #7	$192.51	12.837%	$217.2225	$217.22	$217.20	$217.20
7 purchase totals =	$903.60		$981.1302	$981.13	$981.10	$981.10