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	$182.55	7.377%	$196.0167	$196.02	$196.00	$196.00
Purchase #2	$208.26	12.156%	$233.5761	$233.58	$233.60	$233.60
Purchase #3	$234.83	13.553%	$266.6565	$266.66	$266.65	$266.70
Purchase #4	$118.52	10.556%	$131.031	$131.03	$131.05	$131.00
Purchase #5	$117.56	13.248%	$133.1343	$133.13	$133.15	$133.10
Purchase #6	$110.76	11.639%	$123.6514	$123.65	$123.65	$123.70
Purchase #7	$130.54	6.497%	$139.0212	$139.02	$139.00	$139.00
7 purchase totals =	$1,103.02		$1,223.0872	$1,223.09	$1,223.10	$1,223.10