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	$195.49	13.660%	$222.1939	$222.19	$222.20	$222.20
Purchase #2	$215.39	10.681%	$238.3958	$238.40	$238.40	$238.40
Purchase #3	$223.58	5.227%	$235.2665	$235.27	$235.25	$235.30
Purchase #4	$28.88	3.423%	$29.8686	$29.87	$29.85	$29.90
Purchase #5	$123.77	3.240%	$127.7801	$127.78	$127.80	$127.80
Purchase #6	$248.85	11.685%	$277.9281	$277.93	$277.95	$277.90
Purchase #7	$59.83	11.134%	$66.4915	$66.49	$66.50	$66.50
7 purchase totals =	$1,095.79		$1,197.9245	$1,197.93	$1,197.95	$1,198.00