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	$105.60	5.542%	$111.4524	$111.45	$111.45	$111.50
Purchase #2	$130.81	5.784%	$138.3761	$138.38	$138.40	$138.40
Purchase #3	$6.42	5.228%	$6.7556	$6.76	$6.75	$6.80
Purchase #4	$102.55	9.131%	$111.9138	$111.91	$111.90	$111.90
Purchase #5	$228.83	4.813%	$239.8436	$239.84	$239.85	$239.80
Purchase #6	$168.76	3.805%	$175.1813	$175.18	$175.20	$175.20
Purchase #7	$20.72	13.122%	$23.4389	$23.44	$23.45	$23.40
7 purchase totals =	$763.69		$806.9617	$806.96	$807.00	$807.00