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	$85.88	5.425%	$90.539	$90.54	$90.55	$90.50
Purchase #2	$151.73	8.178%	$164.1385	$164.14	$164.15	$164.10
Purchase #3	$33.77	8.400%	$36.6067	$36.61	$36.60	$36.60
Purchase #4	$40.65	10.644%	$44.9768	$44.98	$45.00	$45.00
Purchase #5	$22.83	8.446%	$24.7582	$24.76	$24.75	$24.80
Purchase #6	$239.86	9.273%	$262.1022	$262.10	$262.10	$262.10
Purchase #7	$138.90	9.619%	$152.2608	$152.26	$152.25	$152.30
7 purchase totals =	$713.62		$775.3822	$775.39	$775.40	$775.40