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	$58.52	9.127%	$63.8611	$63.86	$63.85	$63.90
Purchase #2	$156.66	10.602%	$173.2691	$173.27	$173.25	$173.30
Purchase #3	$163.93	5.152%	$172.3757	$172.38	$172.40	$172.40
Purchase #4	$219.29	9.848%	$240.8857	$240.89	$240.90	$240.90
Purchase #5	$193.56	8.558%	$210.1249	$210.12	$210.10	$210.10
Purchase #6	$152.43	9.757%	$167.3026	$167.30	$167.30	$167.30
Purchase #7	$68.80	12.462%	$77.3739	$77.37	$77.35	$77.40
7 purchase totals =	$1,013.19		$1,105.1930	$1,105.19	$1,105.15	$1,105.30