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	$218.29	4.382%	$227.8555	$227.86	$227.85	$227.90
Purchase #2	$223.92	13.660%	$254.5075	$254.51	$254.50	$254.50
Purchase #3	$114.93	10.686%	$127.2114	$127.21	$127.20	$127.20
Purchase #4	$97.54	3.224%	$100.6847	$100.68	$100.70	$100.70
Purchase #5	$117.60	10.107%	$129.4858	$129.49	$129.50	$129.50
Purchase #6	$21.92	13.476%	$24.8739	$24.87	$24.85	$24.90
Purchase #7	$189.41	12.841%	$213.7321	$213.73	$213.75	$213.70
7 purchase totals =	$983.61		$1,078.3509	$1,078.35	$1,078.35	$1,078.40