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	$93.55	12.172%	$104.9369	$104.94	$104.95	$104.90
Purchase #2	$103.91	4.286%	$108.3636	$108.36	$108.35	$108.40
Purchase #3	$138.49	4.867%	$145.2303	$145.23	$145.25	$145.20
Purchase #4	$76.68	7.468%	$82.4065	$82.41	$82.40	$82.40
Purchase #5	$101.33	9.866%	$111.3272	$111.33	$111.35	$111.30
Purchase #6	$241.28	6.393%	$256.705	$256.71	$256.70	$256.70
Purchase #7	$71.74	13.849%	$81.6753	$81.68	$81.70	$81.70
7 purchase totals =	$826.98		$890.6448	$890.66	$890.70	$890.60