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	$10.77	13.745%	$12.2503	$12.25	$12.25	$12.30
Purchase #2	$214.62	8.864%	$233.6439	$233.64	$233.65	$233.60
Purchase #3	$145.70	12.655%	$164.1383	$164.14	$164.15	$164.10
Purchase #4	$114.70	7.494%	$123.2956	$123.30	$123.30	$123.30
Purchase #5	$219.31	3.684%	$227.3894	$227.39	$227.40	$227.40
Purchase #6	$65.42	10.149%	$72.0595	$72.06	$72.05	$72.10
Purchase #7	$213.61	7.346%	$229.3018	$229.30	$229.30	$229.30
7 purchase totals =	$984.13		$1,062.0788	$1,062.08	$1,062.10	$1,062.10