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	$117.36	8.508%	$127.345	$127.35	$127.35	$127.30
Purchase #2	$90.96	13.607%	$103.3369	$103.34	$103.35	$103.30
Purchase #3	$164.36	10.558%	$181.7131	$181.71	$181.70	$181.70
Purchase #4	$37.68	13.556%	$42.7879	$42.79	$42.80	$42.80
Purchase #5	$40.35	9.250%	$44.0824	$44.08	$44.10	$44.10
Purchase #6	$194.73	5.405%	$205.2552	$205.26	$205.25	$205.30
Purchase #7	$211.32	3.187%	$218.0548	$218.05	$218.05	$218.10
7 purchase totals =	$856.76		$922.5753	$922.58	$922.60	$922.60