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	$177.46	13.283%	$201.032	$201.03	$201.05	$201.00
Purchase #2	$212.27	10.168%	$233.8536	$233.85	$233.85	$233.90
Purchase #3	$52.96	13.295%	$60.001	$60.00	$60.00	$60.00
Purchase #4	$105.99	5.343%	$111.653	$111.65	$111.65	$111.70
Purchase #5	$168.59	6.615%	$179.7422	$179.74	$179.75	$179.70
Purchase #6	$81.78	10.784%	$90.5992	$90.60	$90.60	$90.60
Purchase #7	$121.72	5.586%	$128.5193	$128.52	$128.50	$128.50
7 purchase totals =	$920.77		$1,005.4003	$1,005.39	$1,005.40	$1,005.40