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	$115.28	13.140%	$130.4278	$130.43	$130.45	$130.40
Purchase #2	$65.50	11.258%	$72.874	$72.87	$72.85	$72.90
Purchase #3	$72.42	7.510%	$77.8587	$77.86	$77.85	$77.90
Purchase #4	$123.48	6.768%	$131.8371	$131.84	$131.85	$131.80
Purchase #5	$50.70	4.663%	$53.0641	$53.06	$53.05	$53.10
Purchase #6	$208.60	12.323%	$234.3058	$234.31	$234.30	$234.30
Purchase #7	$12.28	3.678%	$12.7317	$12.73	$12.75	$12.70
7 purchase totals =	$648.26		$713.0992	$713.10	$713.10	$713.10