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	$162.94	6.340%	$173.2704	$173.27	$173.25	$173.30
Purchase #2	$170.54	13.108%	$192.8944	$192.89	$192.90	$192.90
Purchase #3	$134.65	3.525%	$139.3964	$139.40	$139.40	$139.40
Purchase #4	$63.40	5.333%	$66.7811	$66.78	$66.80	$66.80
Purchase #5	$238.28	5.207%	$250.6872	$250.69	$250.70	$250.70
Purchase #6	$207.46	4.798%	$217.4139	$217.41	$217.40	$217.40
Purchase #7	$70.47	3.433%	$72.8892	$72.89	$72.90	$72.90
7 purchase totals =	$1,047.74		$1,113.3326	$1,113.33	$1,113.35	$1,113.40