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	$172.34	7.330%	$184.9725	$184.97	$184.95	$185.00
Purchase #2	$145.49	8.865%	$158.3877	$158.39	$158.40	$158.40
Purchase #3	$248.96	5.164%	$261.8163	$261.82	$261.80	$261.80
Purchase #4	$54.25	13.569%	$61.6112	$61.61	$61.60	$61.60
Purchase #5	$118.82	9.739%	$130.3919	$130.39	$130.40	$130.40
Purchase #6	$22.94	6.159%	$24.3529	$24.35	$24.35	$24.40
Purchase #7	$52.71	3.363%	$54.4826	$54.48	$54.50	$54.50
7 purchase totals =	$815.51		$876.0151	$876.01	$876.00	$876.10