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	$160.39	7.585%	$172.5556	$172.56	$172.55	$172.60
Purchase #2	$78.42	11.568%	$87.4916	$87.49	$87.50	$87.50
Purchase #3	$151.35	7.446%	$162.6195	$162.62	$162.60	$162.60
Purchase #4	$45.37	13.528%	$51.5077	$51.51	$51.50	$51.50
Purchase #5	$182.56	3.753%	$189.4115	$189.41	$189.40	$189.40
Purchase #6	$226.72	9.602%	$248.4897	$248.49	$248.50	$248.50
Purchase #7	$230.34	13.835%	$262.2075	$262.21	$262.20	$262.20
7 purchase totals =	$1,075.15		$1,174.2831	$1,174.29	$1,174.25	$1,174.30