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	$208.26	4.144%	$216.8903	$216.89	$216.90	$216.90
Purchase #2	$138.41	13.274%	$156.7825	$156.78	$156.80	$156.80
Purchase #3	$12.52	13.639%	$14.2276	$14.23	$14.25	$14.20
Purchase #4	$194.91	10.389%	$215.1592	$215.16	$215.15	$215.20
Purchase #5	$166.98	9.229%	$182.3906	$182.39	$182.40	$182.40
Purchase #6	$52.49	8.320%	$56.8572	$56.86	$56.85	$56.90
Purchase #7	$231.81	10.373%	$255.8557	$255.86	$255.85	$255.90
7 purchase totals =	$1,005.38		$1,098.1631	$1,098.17	$1,098.20	$1,098.30