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	$85.52	8.152%	$92.4916	$92.49	$92.50	$92.50
Purchase #2	$103.77	3.684%	$107.5929	$107.59	$107.60	$107.60
Purchase #3	$48.42	13.808%	$55.1058	$55.11	$55.10	$55.10
Purchase #4	$219.88	8.531%	$238.638	$238.64	$238.65	$238.60
Purchase #5	$172.90	8.564%	$187.7072	$187.71	$187.70	$187.70
Purchase #6	$92.60	11.514%	$103.262	$103.26	$103.25	$103.30
Purchase #7	$129.39	9.518%	$141.7053	$141.71	$141.70	$141.70
7 purchase totals =	$852.48		$926.5028	$926.51	$926.50	$926.50