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	$73.75	6.536%	$78.5703	$78.57	$78.55	$78.60
Purchase #2	$242.79	5.278%	$255.6045	$255.60	$255.60	$255.60
Purchase #3	$193.48	3.649%	$200.5401	$200.54	$200.55	$200.50
Purchase #4	$214.38	7.318%	$230.0683	$230.07	$230.05	$230.10
Purchase #5	$74.41	10.794%	$82.4418	$82.44	$82.45	$82.40
Purchase #6	$47.35	7.547%	$50.9235	$50.92	$50.90	$50.90
Purchase #7	$103.76	6.371%	$110.3705	$110.37	$110.35	$110.40
7 purchase totals =	$949.92		$1,008.5190	$1,008.51	$1,008.45	$1,008.50