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	$167.30	3.493%	$173.1438	$173.14	$173.15	$173.10
Purchase #2	$179.66	12.718%	$202.5092	$202.51	$202.50	$202.50
Purchase #3	$42.71	13.742%	$48.5792	$48.58	$48.60	$48.60
Purchase #4	$80.76	5.764%	$85.415	$85.42	$85.40	$85.40
Purchase #5	$39.70	7.158%	$42.5417	$42.54	$42.55	$42.50
Purchase #6	$65.51	3.310%	$67.6784	$67.68	$67.70	$67.70
Purchase #7	$138.25	4.664%	$144.698	$144.70	$144.70	$144.70
7 purchase totals =	$713.89		$764.5653	$764.57	$764.60	$764.50