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	$230.93	10.631%	$255.4802	$255.48	$255.50	$255.50
Purchase #2	$11.82	10.552%	$13.0672	$13.07	$13.05	$13.10
Purchase #3	$147.30	13.285%	$166.8688	$166.87	$166.85	$166.90
Purchase #4	$101.43	5.356%	$106.8626	$106.86	$106.85	$106.90
Purchase #5	$37.25	3.728%	$38.6387	$38.64	$38.65	$38.60
Purchase #6	$200.85	11.328%	$223.6023	$223.60	$223.60	$223.60
Purchase #7	$144.41	5.361%	$152.1518	$152.15	$152.15	$152.20
7 purchase totals =	$873.99		$956.6716	$956.67	$956.65	$956.80