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	$166.95	13.132%	$188.8739	$188.87	$188.85	$188.90
Purchase #2	$61.41	11.350%	$68.38	$68.38	$68.40	$68.40
Purchase #3	$106.95	5.544%	$112.8793	$112.88	$112.90	$112.90
Purchase #4	$65.52	3.152%	$67.5852	$67.59	$67.60	$67.60
Purchase #5	$52.26	7.114%	$55.9778	$55.98	$56.00	$56.00
Purchase #6	$106.36	10.675%	$117.7139	$117.71	$117.70	$117.70
Purchase #7	$62.92	5.557%	$66.4165	$66.42	$66.40	$66.40
7 purchase totals =	$622.37		$677.8266	$677.83	$677.85	$677.90