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	$112.25	6.772%	$119.8516	$119.85	$119.85	$119.90
Purchase #2	$163.59	6.141%	$173.6361	$173.64	$173.65	$173.60
Purchase #3	$163.28	13.801%	$185.8143	$185.81	$185.80	$185.80
Purchase #4	$54.52	3.436%	$56.3933	$56.39	$56.40	$56.40
Purchase #5	$46.46	13.266%	$52.6234	$52.62	$52.60	$52.60
Purchase #6	$32.60	9.258%	$35.6181	$35.62	$35.60	$35.60
Purchase #7	$165.43	8.527%	$179.5362	$179.54	$179.55	$179.50
7 purchase totals =	$738.13		$803.4730	$803.47	$803.45	$803.40