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	$205.68	11.630%	$229.6006	$229.60	$229.60	$229.60
Purchase #2	$26.78	4.183%	$27.9002	$27.90	$27.90	$27.90
Purchase #3	$147.32	9.457%	$161.2521	$161.25	$161.25	$161.30
Purchase #4	$175.41	11.223%	$195.0963	$195.10	$195.10	$195.10
Purchase #5	$156.55	10.149%	$172.4383	$172.44	$172.45	$172.40
Purchase #6	$117.51	5.194%	$123.6135	$123.61	$123.60	$123.60
Purchase #7	$123.44	12.840%	$139.2897	$139.29	$139.30	$139.30
7 purchase totals =	$952.69		$1,049.1907	$1,049.19	$1,049.20	$1,049.20