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	$233.73	8.653%	$253.9547	$253.95	$253.95	$254.00
Purchase #2	$84.93	11.360%	$94.578	$94.58	$94.60	$94.60
Purchase #3	$183.79	7.156%	$196.942	$196.94	$196.95	$196.90
Purchase #4	$128.51	11.810%	$143.687	$143.69	$143.70	$143.70
Purchase #5	$153.81	5.845%	$162.8002	$162.80	$162.80	$162.80
Purchase #6	$90.42	11.250%	$100.5923	$100.59	$100.60	$100.60
Purchase #7	$55.43	9.783%	$60.8527	$60.85	$60.85	$60.90
7 purchase totals =	$930.62		$1,013.4069	$1,013.40	$1,013.45	$1,013.50