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	$153.36	9.107%	$167.3265	$167.33	$167.35	$167.30
Purchase #2	$152.72	7.593%	$164.316	$164.32	$164.30	$164.30
Purchase #3	$118.42	4.201%	$123.3948	$123.39	$123.40	$123.40
Purchase #4	$10.73	6.426%	$11.4195	$11.42	$11.40	$11.40
Purchase #5	$188.75	10.825%	$209.1822	$209.18	$209.20	$209.20
Purchase #6	$47.63	8.805%	$51.8238	$51.82	$51.80	$51.80
Purchase #7	$10.27	8.624%	$11.1557	$11.16	$11.15	$11.20
7 purchase totals =	$681.88		$738.6185	$738.62	$738.60	$738.60