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	$201.65	4.788%	$211.305	$211.31	$211.30	$211.30
Purchase #2	$152.69	9.181%	$166.7085	$166.71	$166.70	$166.70
Purchase #3	$32.84	13.114%	$37.1466	$37.15	$37.15	$37.10
Purchase #4	$52.43	7.773%	$56.5054	$56.51	$56.50	$56.50
Purchase #5	$73.34	4.250%	$76.457	$76.46	$76.45	$76.50
Purchase #6	$102.87	13.370%	$116.6237	$116.62	$116.60	$116.60
Purchase #7	$15.54	13.188%	$17.5894	$17.59	$17.60	$17.60
7 purchase totals =	$631.36		$682.3356	$682.35	$682.30	$682.30