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	$205.37	8.540%	$222.9086	$222.91	$222.90	$222.90
Purchase #2	$86.72	6.267%	$92.1547	$92.15	$92.15	$92.20
Purchase #3	$138.68	4.358%	$144.7237	$144.72	$144.70	$144.70
Purchase #4	$226.77	10.331%	$250.1976	$250.20	$250.20	$250.20
Purchase #5	$99.58	13.343%	$112.867	$112.87	$112.85	$112.90
Purchase #6	$50.94	5.413%	$53.6974	$53.70	$53.70	$53.70
Purchase #7	$156.83	3.381%	$162.1324	$162.13	$162.15	$162.10
7 purchase totals =	$964.89		$1,038.6814	$1,038.68	$1,038.65	$1,038.70