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	$153.96	5.194%	$161.9567	$161.96	$161.95	$162.00
Purchase #2	$96.69	13.372%	$109.6194	$109.62	$109.60	$109.60
Purchase #3	$201.32	13.570%	$228.6391	$228.64	$228.65	$228.60
Purchase #4	$100.30	12.166%	$112.5025	$112.50	$112.50	$112.50
Purchase #5	$132.93	10.317%	$146.6444	$146.64	$146.65	$146.60
Purchase #6	$235.91	9.190%	$257.5901	$257.59	$257.60	$257.60
Purchase #7	$47.72	13.278%	$54.0563	$54.06	$54.05	$54.10
7 purchase totals =	$968.83		$1,071.0085	$1,071.01	$1,071.00	$1,071.00