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	$230.34	13.770%	$262.0578	$262.06	$262.05	$262.10
Purchase #2	$112.83	10.451%	$124.6219	$124.62	$124.60	$124.60
Purchase #3	$43.48	9.319%	$47.5319	$47.53	$47.55	$47.50
Purchase #4	$171.47	10.436%	$189.3646	$189.36	$189.35	$189.40
Purchase #5	$129.94	9.808%	$142.6845	$142.68	$142.70	$142.70
Purchase #6	$54.93	7.825%	$59.2283	$59.23	$59.25	$59.20
Purchase #7	$51.82	6.784%	$55.3355	$55.34	$55.35	$55.30
7 purchase totals =	$794.81		$880.8245	$880.82	$880.85	$880.80