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	$207.39	4.432%	$216.5815	$216.58	$216.60	$216.60
Purchase #2	$9.36	8.290%	$10.1359	$10.14	$10.15	$10.10
Purchase #3	$70.86	10.701%	$78.4427	$78.44	$78.45	$78.40
Purchase #4	$48.87	5.169%	$51.3961	$51.40	$51.40	$51.40
Purchase #5	$85.67	3.406%	$88.5879	$88.59	$88.60	$88.60
Purchase #6	$37.69	10.461%	$41.6328	$41.63	$41.65	$41.60
Purchase #7	$56.60	4.596%	$59.2013	$59.20	$59.20	$59.20
7 purchase totals =	$516.44		$545.9782	$545.98	$546.05	$545.90