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	$89.36	7.116%	$95.7189	$95.72	$95.70	$95.70
Purchase #2	$138.61	4.182%	$144.4067	$144.41	$144.40	$144.40
Purchase #3	$19.82	4.556%	$20.723	$20.72	$20.70	$20.70
Purchase #4	$138.60	7.591%	$149.1211	$149.12	$149.10	$149.10
Purchase #5	$21.54	11.858%	$24.0942	$24.09	$24.10	$24.10
Purchase #6	$53.29	12.261%	$59.8239	$59.82	$59.80	$59.80
Purchase #7	$177.60	8.508%	$192.7102	$192.71	$192.70	$192.70
7 purchase totals =	$638.82		$686.5980	$686.59	$686.50	$686.50