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	$38.81	11.490%	$43.2693	$43.27	$43.25	$43.30
Purchase #2	$153.49	7.845%	$165.5313	$165.53	$165.55	$165.50
Purchase #3	$231.50	4.513%	$241.9476	$241.95	$241.95	$241.90
Purchase #4	$64.56	13.507%	$73.2801	$73.28	$73.30	$73.30
Purchase #5	$71.82	9.346%	$78.5323	$78.53	$78.55	$78.50
Purchase #6	$85.25	5.785%	$90.1817	$90.18	$90.20	$90.20
Purchase #7	$195.39	10.242%	$215.4018	$215.40	$215.40	$215.40
7 purchase totals =	$840.82		$908.1441	$908.14	$908.20	$908.10