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	$157.92	9.282%	$172.5781	$172.58	$172.60	$172.60
Purchase #2	$153.75	12.110%	$172.3691	$172.37	$172.35	$172.40
Purchase #3	$173.27	4.481%	$181.0342	$181.03	$181.05	$181.00
Purchase #4	$177.82	10.618%	$196.7009	$196.70	$196.70	$196.70
Purchase #5	$215.46	12.274%	$241.9056	$241.91	$241.90	$241.90
Purchase #6	$156.65	10.846%	$173.6403	$173.64	$173.65	$173.60
Purchase #7	$158.74	6.329%	$168.7867	$168.79	$168.80	$168.80
7 purchase totals =	$1,193.61		$1,307.0149	$1,307.02	$1,307.05	$1,307.00