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	$157.98	8.840%	$171.9454	$171.95	$171.95	$171.90
Purchase #2	$220.71	12.284%	$247.822	$247.82	$247.80	$247.80
Purchase #3	$100.39	5.208%	$105.6183	$105.62	$105.60	$105.60
Purchase #4	$94.51	10.297%	$104.2417	$104.24	$104.25	$104.20
Purchase #5	$229.46	3.490%	$237.4682	$237.47	$237.45	$237.50
Purchase #6	$56.55	5.112%	$59.4408	$59.44	$59.45	$59.40
Purchase #7	$133.83	9.566%	$146.6322	$146.63	$146.65	$146.60
7 purchase totals =	$993.43		$1,073.1686	$1,073.17	$1,073.15	$1,073.00