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	$181.38	13.559%	$205.9733	$205.97	$205.95	$206.00
Purchase #2	$27.45	5.140%	$28.8609	$28.86	$28.85	$28.90
Purchase #3	$132.80	6.225%	$141.0668	$141.07	$141.05	$141.10
Purchase #4	$250.93	8.151%	$271.3833	$271.38	$271.40	$271.40
Purchase #5	$142.48	12.686%	$160.555	$160.56	$160.55	$160.60
Purchase #6	$53.50	7.484%	$57.5039	$57.50	$57.50	$57.50
Purchase #7	$133.64	7.249%	$143.3276	$143.33	$143.35	$143.30
7 purchase totals =	$922.18		$1,008.6708	$1,008.67	$1,008.65	$1,008.80