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	$224.48	7.665%	$241.6864	$241.69	$241.70	$241.70
Purchase #2	$153.40	3.744%	$159.1433	$159.14	$159.15	$159.10
Purchase #3	$164.80	6.713%	$175.863	$175.86	$175.85	$175.90
Purchase #4	$166.66	3.560%	$172.5931	$172.59	$172.60	$172.60
Purchase #5	$124.39	7.327%	$133.5041	$133.50	$133.50	$133.50
Purchase #6	$94.55	10.301%	$104.2896	$104.29	$104.30	$104.30
Purchase #7	$75.62	5.152%	$79.5159	$79.52	$79.50	$79.50
7 purchase totals =	$1,003.90		$1,066.5954	$1,066.59	$1,066.60	$1,066.60