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	$196.90	10.412%	$217.4012	$217.40	$217.40	$217.40
Purchase #2	$41.69	6.377%	$44.3486	$44.35	$44.35	$44.30
Purchase #3	$135.87	6.743%	$145.0317	$145.03	$145.05	$145.00
Purchase #4	$153.51	9.635%	$168.3007	$168.30	$168.30	$168.30
Purchase #5	$41.27	3.757%	$42.8205	$42.82	$42.80	$42.80
Purchase #6	$147.27	9.388%	$161.0957	$161.10	$161.10	$161.10
Purchase #7	$61.30	6.763%	$65.4457	$65.45	$65.45	$65.40
7 purchase totals =	$777.81		$844.4441	$844.45	$844.45	$844.30