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	$159.28	9.394%	$174.2428	$174.24	$174.25	$174.20
Purchase #2	$90.73	13.781%	$103.2335	$103.23	$103.25	$103.20
Purchase #3	$176.25	7.435%	$189.3542	$189.35	$189.35	$189.40
Purchase #4	$91.82	10.257%	$101.238	$101.24	$101.25	$101.20
Purchase #5	$123.80	3.323%	$127.9139	$127.91	$127.90	$127.90
Purchase #6	$106.95	6.676%	$114.09	$114.09	$114.10	$114.10
Purchase #7	$153.86	5.627%	$162.5177	$162.52	$162.50	$162.50
7 purchase totals =	$902.69		$972.5901	$972.58	$972.60	$972.50