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	$210.52	6.143%	$223.4522	$223.45	$223.45	$223.50
Purchase #2	$96.36	4.491%	$100.6875	$100.69	$100.70	$100.70
Purchase #3	$41.41	13.190%	$46.872	$46.87	$46.85	$46.90
Purchase #4	$241.97	7.304%	$259.6435	$259.64	$259.65	$259.60
Purchase #5	$12.99	3.307%	$13.4196	$13.42	$13.40	$13.40
Purchase #6	$164.69	9.373%	$180.1264	$180.13	$180.15	$180.10
Purchase #7	$73.76	6.818%	$78.789	$78.79	$78.80	$78.80
7 purchase totals =	$841.70		$902.9902	$902.99	$903.00	$903.00