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	$131.50	11.484%	$146.6015	$146.60	$146.60	$146.60
Purchase #2	$133.78	10.654%	$148.0329	$148.03	$148.05	$148.00
Purchase #3	$144.40	12.685%	$162.7171	$162.72	$162.70	$162.70
Purchase #4	$66.70	12.460%	$75.0108	$75.01	$75.00	$75.00
Purchase #5	$207.60	3.717%	$215.3165	$215.32	$215.30	$215.30
Purchase #6	$173.86	6.640%	$185.4043	$185.40	$185.40	$185.40
Purchase #7	$132.93	13.551%	$150.9433	$150.94	$150.95	$150.90
7 purchase totals =	$990.77		$1,084.0264	$1,084.02	$1,084.00	$1,083.90