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	$115.46	6.547%	$123.0192	$123.02	$123.00	$123.00
Purchase #2	$90.88	10.734%	$100.6351	$100.64	$100.65	$100.60
Purchase #3	$79.49	5.278%	$83.6855	$83.69	$83.70	$83.70
Purchase #4	$173.89	3.816%	$180.5256	$180.53	$180.55	$180.50
Purchase #5	$195.34	9.585%	$214.0633	$214.06	$214.05	$214.10
Purchase #6	$172.70	5.179%	$181.6441	$181.64	$181.65	$181.60
Purchase #7	$44.58	10.780%	$49.3857	$49.39	$49.40	$49.40
7 purchase totals =	$872.34		$932.9585	$932.97	$933.00	$932.90