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	$153.61	12.764%	$173.2168	$173.22	$173.20	$173.20
Purchase #2	$166.47	4.157%	$173.3902	$173.39	$173.40	$173.40
Purchase #3	$75.41	6.653%	$80.427	$80.43	$80.45	$80.40
Purchase #4	$175.37	4.498%	$183.2581	$183.26	$183.25	$183.30
Purchase #5	$75.50	4.305%	$78.7503	$78.75	$78.75	$78.80
Purchase #6	$141.40	12.158%	$158.5914	$158.59	$158.60	$158.60
Purchase #7	$167.76	6.127%	$178.0387	$178.04	$178.05	$178.00
7 purchase totals =	$955.52		$1,025.6725	$1,025.68	$1,025.70	$1,025.70