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	$86.51	4.510%	$90.4116	$90.41	$90.40	$90.40
Purchase #2	$124.37	5.128%	$130.7477	$130.75	$130.75	$130.70
Purchase #3	$57.45	3.711%	$59.582	$59.58	$59.60	$59.60
Purchase #4	$190.67	8.121%	$206.1543	$206.15	$206.15	$206.20
Purchase #5	$186.66	6.392%	$198.5913	$198.59	$198.60	$198.60
Purchase #6	$232.81	12.739%	$262.4677	$262.47	$262.45	$262.50
Purchase #7	$230.27	11.758%	$257.3451	$257.35	$257.35	$257.30
7 purchase totals =	$1,108.74		$1,205.2997	$1,205.30	$1,205.30	$1,205.30