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	$141.64	9.443%	$155.0151	$155.02	$155.00	$155.00
Purchase #2	$13.85	3.289%	$14.3055	$14.31	$14.30	$14.30
Purchase #3	$155.72	13.830%	$177.2561	$177.26	$177.25	$177.30
Purchase #4	$98.75	13.124%	$111.71	$111.71	$111.70	$111.70
Purchase #5	$138.87	4.111%	$144.5789	$144.58	$144.60	$144.60
Purchase #6	$199.35	9.180%	$217.6503	$217.65	$217.65	$217.70
Purchase #7	$165.47	11.528%	$184.5454	$184.55	$184.55	$184.50
7 purchase totals =	$913.65		$1,005.0613	$1,005.08	$1,005.05	$1,005.10