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	$205.39	11.654%	$229.3262	$229.33	$229.35	$229.30
Purchase #2	$245.52	8.356%	$266.0357	$266.04	$266.05	$266.00
Purchase #3	$174.32	9.233%	$190.415	$190.42	$190.40	$190.40
Purchase #4	$109.79	12.147%	$123.1262	$123.13	$123.15	$123.10
Purchase #5	$208.52	4.442%	$217.7825	$217.78	$217.80	$217.80
Purchase #6	$145.77	13.698%	$165.7376	$165.74	$165.75	$165.70
Purchase #7	$160.27	5.705%	$169.4134	$169.41	$169.40	$169.40
7 purchase totals =	$1,249.58		$1,361.8366	$1,361.85	$1,361.90	$1,361.70