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	$101.37	12.597%	$114.1396	$114.14	$114.15	$114.10
Purchase #2	$243.35	5.134%	$255.8436	$255.84	$255.85	$255.80
Purchase #3	$234.60	10.509%	$259.2541	$259.25	$259.25	$259.30
Purchase #4	$9.53	7.636%	$10.2577	$10.26	$10.25	$10.30
Purchase #5	$231.39	12.821%	$261.0565	$261.06	$261.05	$261.10
Purchase #6	$78.53	5.164%	$82.5853	$82.59	$82.60	$82.60
Purchase #7	$21.96	12.610%	$24.7292	$24.73	$24.75	$24.70
7 purchase totals =	$920.73		$1,007.8660	$1,007.87	$1,007.90	$1,007.90