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	$140.94	12.368%	$158.3715	$158.37	$158.35	$158.40
Purchase #2	$40.28	11.459%	$44.8957	$44.90	$44.90	$44.90
Purchase #3	$233.32	5.233%	$245.5296	$245.53	$245.55	$245.50
Purchase #4	$130.51	5.677%	$137.9191	$137.92	$137.90	$137.90
Purchase #5	$33.72	13.712%	$38.3437	$38.34	$38.35	$38.30
Purchase #6	$17.88	10.787%	$19.8087	$19.81	$19.80	$19.80
Purchase #7	$108.52	12.173%	$121.7301	$121.73	$121.75	$121.70
7 purchase totals =	$705.17		$766.5984	$766.60	$766.60	$766.50