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	$218.87	7.553%	$235.4013	$235.40	$235.40	$235.40
Purchase #2	$103.59	7.466%	$111.324	$111.32	$111.30	$111.30
Purchase #3	$5.69	6.480%	$6.0587	$6.06	$6.05	$6.10
Purchase #4	$235.29	12.587%	$264.906	$264.91	$264.90	$264.90
Purchase #5	$17.73	10.403%	$19.5745	$19.57	$19.55	$19.60
Purchase #6	$147.97	7.189%	$158.6076	$158.61	$158.60	$158.60
Purchase #7	$104.72	4.442%	$109.3717	$109.37	$109.35	$109.40
7 purchase totals =	$833.86		$905.2438	$905.24	$905.15	$905.30