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	$183.58	8.111%	$198.4702	$198.47	$198.45	$198.50
Purchase #2	$220.63	5.691%	$233.1861	$233.19	$233.20	$233.20
Purchase #3	$37.72	8.631%	$40.9756	$40.98	$41.00	$41.00
Purchase #4	$83.81	7.829%	$90.3715	$90.37	$90.35	$90.40
Purchase #5	$237.62	5.601%	$250.9291	$250.93	$250.95	$250.90
Purchase #6	$46.84	6.487%	$49.8785	$49.88	$49.90	$49.90
Purchase #7	$130.55	5.418%	$137.6232	$137.62	$137.60	$137.60
7 purchase totals =	$940.75		$1,001.4342	$1,001.44	$1,001.45	$1,001.50