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	$53.77	9.866%	$59.0749	$59.07	$59.05	$59.10
Purchase #2	$89.68	10.659%	$99.239	$99.24	$99.25	$99.20
Purchase #3	$222.94	3.116%	$229.8868	$229.89	$229.90	$229.90
Purchase #4	$112.79	6.539%	$120.1653	$120.17	$120.15	$120.20
Purchase #5	$18.35	5.505%	$19.3602	$19.36	$19.35	$19.40
Purchase #6	$152.71	7.685%	$164.4458	$164.45	$164.45	$164.40
Purchase #7	$193.40	5.182%	$203.422	$203.42	$203.40	$203.40
7 purchase totals =	$843.64		$895.5940	$895.60	$895.55	$895.60