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	$96.97	10.627%	$107.275	$107.28	$107.30	$107.30
Purchase #2	$134.35	13.779%	$152.8621	$152.86	$152.85	$152.90
Purchase #3	$238.52	9.749%	$261.7733	$261.77	$261.75	$261.80
Purchase #4	$128.58	7.795%	$138.6028	$138.60	$138.60	$138.60
Purchase #5	$222.50	11.756%	$248.6571	$248.66	$248.65	$248.70
Purchase #6	$96.49	7.321%	$103.554	$103.55	$103.55	$103.60
Purchase #7	$82.69	9.430%	$90.4877	$90.49	$90.50	$90.50
7 purchase totals =	$1,000.10		$1,103.2120	$1,103.21	$1,103.20	$1,103.40