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	$141.72	11.715%	$158.3225	$158.32	$158.30	$158.30
Purchase #2	$156.85	10.340%	$173.0683	$173.07	$173.05	$173.10
Purchase #3	$114.65	11.536%	$127.876	$127.88	$127.90	$127.90
Purchase #4	$83.75	13.224%	$94.8251	$94.83	$94.85	$94.80
Purchase #5	$203.77	11.551%	$227.3075	$227.31	$227.30	$227.30
Purchase #6	$218.40	9.865%	$239.9452	$239.95	$239.95	$239.90
Purchase #7	$207.38	13.467%	$235.3079	$235.31	$235.30	$235.30
7 purchase totals =	$1,126.52		$1,256.6525	$1,256.67	$1,256.65	$1,256.60