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	$125.32	5.748%	$132.5234	$132.52	$132.50	$132.50
Purchase #2	$125.62	13.114%	$142.0938	$142.09	$142.10	$142.10
Purchase #3	$180.74	4.338%	$188.5805	$188.58	$188.60	$188.60
Purchase #4	$78.91	3.132%	$81.3815	$81.38	$81.40	$81.40
Purchase #5	$54.90	11.283%	$61.0944	$61.09	$61.10	$61.10
Purchase #6	$47.85	11.854%	$53.5221	$53.52	$53.50	$53.50
Purchase #7	$142.40	11.682%	$159.0352	$159.04	$159.05	$159.00
7 purchase totals =	$755.74		$818.2309	$818.22	$818.25	$818.20