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	$226.43	12.121%	$253.8756	$253.88	$253.90	$253.90
Purchase #2	$117.50	13.631%	$133.5164	$133.52	$133.50	$133.50
Purchase #3	$14.72	10.616%	$16.2827	$16.28	$16.30	$16.30
Purchase #4	$193.34	5.799%	$204.5518	$204.55	$204.55	$204.60
Purchase #5	$89.38	11.755%	$99.8866	$99.89	$99.90	$99.90
Purchase #6	$99.67	11.461%	$111.0932	$111.09	$111.10	$111.10
Purchase #7	$208.46	8.741%	$226.6815	$226.68	$226.70	$226.70
7 purchase totals =	$949.50		$1,045.8878	$1,045.89	$1,045.95	$1,046.00