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	$229.51	11.558%	$256.0368	$256.04	$256.05	$256.00
Purchase #2	$231.55	11.185%	$257.4489	$257.45	$257.45	$257.40
Purchase #3	$17.27	5.690%	$18.2527	$18.25	$18.25	$18.30
Purchase #4	$67.34	8.268%	$72.9077	$72.91	$72.90	$72.90
Purchase #5	$20.51	7.677%	$22.0846	$22.08	$22.10	$22.10
Purchase #6	$199.43	3.600%	$206.6095	$206.61	$206.60	$206.60
Purchase #7	$223.46	13.500%	$253.6271	$253.63	$253.65	$253.60
7 purchase totals =	$989.07		$1,086.9673	$1,086.97	$1,087.00	$1,086.90