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	$216.47	9.309%	$236.6212	$236.62	$236.60	$236.60
Purchase #2	$9.62	13.592%	$10.9276	$10.93	$10.95	$10.90
Purchase #3	$221.45	7.704%	$238.5105	$238.51	$238.50	$238.50
Purchase #4	$67.71	5.490%	$71.4273	$71.43	$71.45	$71.40
Purchase #5	$203.66	7.136%	$218.1932	$218.19	$218.20	$218.20
Purchase #6	$180.45	4.695%	$188.9221	$188.92	$188.90	$188.90
Purchase #7	$37.37	8.699%	$40.6208	$40.62	$40.60	$40.60
7 purchase totals =	$936.73		$1,005.2227	$1,005.22	$1,005.20	$1,005.10