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	$58.50	12.346%	$65.7224	$65.72	$65.70	$65.70
Purchase #2	$143.65	9.160%	$156.8083	$156.81	$156.80	$156.80
Purchase #3	$233.56	3.442%	$241.5991	$241.60	$241.60	$241.60
Purchase #4	$207.96	11.469%	$231.8109	$231.81	$231.80	$231.80
Purchase #5	$84.87	6.843%	$90.6777	$90.68	$90.70	$90.70
Purchase #6	$201.32	12.368%	$226.2193	$226.22	$226.20	$226.20
Purchase #7	$106.66	4.800%	$111.7797	$111.78	$111.80	$111.80
7 purchase totals =	$1,036.52		$1,124.6174	$1,124.62	$1,124.60	$1,124.60