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	$193.69	13.431%	$219.7045	$219.70	$219.70	$219.70
Purchase #2	$191.78	8.618%	$208.3076	$208.31	$208.30	$208.30
Purchase #3	$89.58	10.766%	$99.2242	$99.22	$99.20	$99.20
Purchase #4	$184.34	7.665%	$198.4697	$198.47	$198.45	$198.50
Purchase #5	$145.61	8.247%	$157.6185	$157.62	$157.60	$157.60
Purchase #6	$44.81	12.784%	$50.5385	$50.54	$50.55	$50.50
Purchase #7	$192.95	9.659%	$211.587	$211.59	$211.60	$211.60
7 purchase totals =	$1,042.76		$1,145.4500	$1,145.45	$1,145.40	$1,145.40