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	$204.94	8.635%	$222.6366	$222.64	$222.65	$222.60
Purchase #2	$116.42	9.298%	$127.2447	$127.24	$127.25	$127.20
Purchase #3	$126.97	11.286%	$141.2998	$141.30	$141.30	$141.30
Purchase #4	$64.85	5.175%	$68.206	$68.21	$68.20	$68.20
Purchase #5	$207.68	6.838%	$221.8812	$221.88	$221.90	$221.90
Purchase #6	$78.77	6.471%	$83.8672	$83.87	$83.85	$83.90
Purchase #7	$237.39	7.525%	$255.2536	$255.25	$255.25	$255.30
7 purchase totals =	$1,037.02		$1,120.3891	$1,120.39	$1,120.40	$1,120.40