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	$215.47	12.243%	$241.85	$241.85	$241.85	$241.90
Purchase #2	$173.46	5.164%	$182.4175	$182.42	$182.40	$182.40
Purchase #3	$13.34	12.869%	$15.0567	$15.06	$15.05	$15.10
Purchase #4	$55.52	7.142%	$59.4852	$59.49	$59.50	$59.50
Purchase #5	$103.25	13.834%	$117.5336	$117.53	$117.55	$117.50
Purchase #6	$6.99	3.189%	$7.2129	$7.21	$7.20	$7.20
Purchase #7	$106.66	5.517%	$112.5444	$112.54	$112.55	$112.50
7 purchase totals =	$674.69		$736.1003	$736.10	$736.10	$736.10