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	$114.82	4.171%	$119.6091	$119.61	$119.60	$119.60
Purchase #2	$124.94	7.527%	$134.3442	$134.34	$134.35	$134.30
Purchase #3	$59.92	8.865%	$65.2319	$65.23	$65.25	$65.20
Purchase #4	$106.30	9.868%	$116.7897	$116.79	$116.80	$116.80
Purchase #5	$247.79	13.516%	$281.2813	$281.28	$281.30	$281.30
Purchase #6	$71.35	13.632%	$81.0764	$81.08	$81.10	$81.10
Purchase #7	$102.71	8.842%	$111.7916	$111.79	$111.80	$111.80
7 purchase totals =	$827.83		$910.1242	$910.12	$910.20	$910.10