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	$63.25	7.602%	$68.0583	$68.06	$68.05	$68.10
Purchase #2	$239.43	9.672%	$262.5877	$262.59	$262.60	$262.60
Purchase #3	$134.38	4.647%	$140.6246	$140.62	$140.60	$140.60
Purchase #4	$132.90	9.401%	$145.3939	$145.39	$145.40	$145.40
Purchase #5	$184.29	6.486%	$196.243	$196.24	$196.25	$196.20
Purchase #6	$40.76	5.762%	$43.1086	$43.11	$43.10	$43.10
Purchase #7	$12.91	5.374%	$13.6038	$13.60	$13.60	$13.60
7 purchase totals =	$807.92		$869.6199	$869.61	$869.60	$869.60