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	$185.62	3.383%	$191.8995	$191.90	$191.90	$191.90
Purchase #2	$24.59	6.823%	$26.2678	$26.27	$26.25	$26.30
Purchase #3	$132.82	9.209%	$145.0514	$145.05	$145.05	$145.10
Purchase #4	$130.25	10.788%	$144.3014	$144.30	$144.30	$144.30
Purchase #5	$143.73	6.461%	$153.0164	$153.02	$153.00	$153.00
Purchase #6	$182.36	6.470%	$194.1587	$194.16	$194.15	$194.20
Purchase #7	$100.40	11.252%	$111.697	$111.70	$111.70	$111.70
7 purchase totals =	$899.77		$966.3922	$966.40	$966.35	$966.50