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	$52.51	9.231%	$57.3572	$57.36	$57.35	$57.40
Purchase #2	$10.47	6.577%	$11.1586	$11.16	$11.15	$11.20
Purchase #3	$112.84	9.526%	$123.5891	$123.59	$123.60	$123.60
Purchase #4	$205.53	8.792%	$223.6002	$223.60	$223.60	$223.60
Purchase #5	$155.56	8.351%	$168.5508	$168.55	$168.55	$168.60
Purchase #6	$22.38	9.810%	$24.5755	$24.58	$24.60	$24.60
Purchase #7	$144.80	12.168%	$162.4193	$162.42	$162.40	$162.40
7 purchase totals =	$704.09		$771.2507	$771.26	$771.25	$771.40