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	$54.46	9.453%	$59.6081	$59.61	$59.60	$59.60
Purchase #2	$76.78	12.456%	$86.3437	$86.34	$86.35	$86.30
Purchase #3	$167.47	7.141%	$179.429	$179.43	$179.45	$179.40
Purchase #4	$91.96	7.197%	$98.5784	$98.58	$98.60	$98.60
Purchase #5	$46.95	12.433%	$52.7873	$52.79	$52.80	$52.80
Purchase #6	$46.65	5.251%	$49.0996	$49.10	$49.10	$49.10
Purchase #7	$10.72	4.810%	$11.2356	$11.24	$11.25	$11.20
7 purchase totals =	$494.99		$537.0817	$537.09	$537.15	$537.00