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	$151.53	12.848%	$170.9986	$171.00	$171.00	$171.00
Purchase #2	$184.43	8.758%	$200.5824	$200.58	$200.60	$200.60
Purchase #3	$165.79	4.582%	$173.3865	$173.39	$173.40	$173.40
Purchase #4	$134.32	13.668%	$152.6789	$152.68	$152.70	$152.70
Purchase #5	$102.49	9.362%	$112.0851	$112.09	$112.10	$112.10
Purchase #6	$95.25	3.242%	$98.338	$98.34	$98.35	$98.30
Purchase #7	$130.51	12.447%	$146.7546	$146.75	$146.75	$146.80
7 purchase totals =	$964.32		$1,054.8241	$1,054.83	$1,054.90	$1,054.90