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	$37.38	12.260%	$41.9628	$41.96	$41.95	$42.00
Purchase #2	$219.47	4.781%	$229.9629	$229.96	$229.95	$230.00
Purchase #3	$49.41	3.256%	$51.0188	$51.02	$51.00	$51.00
Purchase #4	$219.87	4.874%	$230.5865	$230.59	$230.60	$230.60
Purchase #5	$96.73	8.615%	$105.0633	$105.06	$105.05	$105.10
Purchase #6	$246.74	10.406%	$272.4158	$272.42	$272.40	$272.40
Purchase #7	$131.83	8.810%	$143.4442	$143.44	$143.45	$143.40
7 purchase totals =	$1,001.43		$1,074.4543	$1,074.45	$1,074.40	$1,074.50