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	$116.68	5.422%	$123.0064	$123.01	$123.00	$123.00
Purchase #2	$147.38	7.851%	$158.9508	$158.95	$158.95	$159.00
Purchase #3	$169.79	12.796%	$191.5163	$191.52	$191.50	$191.50
Purchase #4	$95.98	5.472%	$101.232	$101.23	$101.25	$101.20
Purchase #5	$197.42	5.732%	$208.7361	$208.74	$208.75	$208.70
Purchase #6	$48.48	10.538%	$53.5888	$53.59	$53.60	$53.60
Purchase #7	$72.35	7.649%	$77.8841	$77.88	$77.90	$77.90
7 purchase totals =	$848.08		$914.9145	$914.92	$914.95	$914.90