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	$100.96	10.492%	$111.5527	$111.55	$111.55	$111.60
Purchase #2	$243.63	10.667%	$269.618	$269.62	$269.60	$269.60
Purchase #3	$9.62	11.213%	$10.6987	$10.70	$10.70	$10.70
Purchase #4	$112.70	13.209%	$127.5865	$127.59	$127.60	$127.60
Purchase #5	$12.27	12.494%	$13.803	$13.80	$13.80	$13.80
Purchase #6	$217.47	6.348%	$231.275	$231.28	$231.30	$231.30
Purchase #7	$226.95	6.378%	$241.4249	$241.42	$241.40	$241.40
7 purchase totals =	$923.60		$1,005.9588	$1,005.96	$1,005.95	$1,006.00