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	$227.55	12.133%	$255.1586	$255.16	$255.15	$255.20
Purchase #2	$99.86	5.585%	$105.4372	$105.44	$105.45	$105.40
Purchase #3	$249.69	11.375%	$278.0922	$278.09	$278.10	$278.10
Purchase #4	$59.52	11.273%	$66.2297	$66.23	$66.25	$66.20
Purchase #5	$54.49	7.546%	$58.6018	$58.60	$58.60	$58.60
Purchase #6	$44.56	10.183%	$49.0975	$49.10	$49.10	$49.10
Purchase #7	$200.36	5.227%	$210.8328	$210.83	$210.85	$210.80
7 purchase totals =	$936.03		$1,023.4498	$1,023.45	$1,023.50	$1,023.40