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	$97.33	8.411%	$105.5164	$105.52	$105.50	$105.50
Purchase #2	$82.58	9.828%	$90.696	$90.70	$90.70	$90.70
Purchase #3	$106.99	5.303%	$112.6637	$112.66	$112.65	$112.70
Purchase #4	$166.89	7.648%	$179.6537	$179.65	$179.65	$179.70
Purchase #5	$75.81	8.349%	$82.1394	$82.14	$82.15	$82.10
Purchase #6	$161.85	4.116%	$168.5117	$168.51	$168.50	$168.50
Purchase #7	$53.28	5.153%	$56.0255	$56.03	$56.05	$56.00
7 purchase totals =	$744.73		$795.2064	$795.21	$795.20	$795.20