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	$19.32	6.627%	$20.6003	$20.60	$20.60	$20.60
Purchase #2	$193.96	7.244%	$208.0105	$208.01	$208.00	$208.00
Purchase #3	$86.82	6.411%	$92.386	$92.39	$92.40	$92.40
Purchase #4	$98.30	4.425%	$102.6498	$102.65	$102.65	$102.60
Purchase #5	$77.93	4.519%	$81.4517	$81.45	$81.45	$81.50
Purchase #6	$193.70	3.363%	$200.2141	$200.21	$200.20	$200.20
Purchase #7	$18.42	13.780%	$20.9583	$20.96	$20.95	$21.00
7 purchase totals =	$688.45		$726.2707	$726.27	$726.25	$726.30