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	$57.87	4.466%	$60.4545	$60.45	$60.45	$60.50
Purchase #2	$28.91	11.524%	$32.2416	$32.24	$32.25	$32.20
Purchase #3	$248.38	5.794%	$262.7711	$262.77	$262.75	$262.80
Purchase #4	$234.71	12.247%	$263.4549	$263.45	$263.45	$263.50
Purchase #5	$102.73	8.658%	$111.6244	$111.62	$111.60	$111.60
Purchase #6	$196.55	5.474%	$207.3091	$207.31	$207.30	$207.30
Purchase #7	$27.86	11.324%	$31.0149	$31.01	$31.00	$31.00
7 purchase totals =	$897.01		$968.8705	$968.85	$968.80	$968.90