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	$139.36	6.278%	$148.109	$148.11	$148.10	$148.10
Purchase #2	$72.79	8.333%	$78.8556	$78.86	$78.85	$78.90
Purchase #3	$56.53	4.506%	$59.0772	$59.08	$59.10	$59.10
Purchase #4	$220.61	4.497%	$230.5308	$230.53	$230.55	$230.50
Purchase #5	$19.57	9.460%	$21.4213	$21.42	$21.40	$21.40
Purchase #6	$76.67	7.546%	$82.4555	$82.46	$82.45	$82.50
Purchase #7	$129.26	11.866%	$144.598	$144.60	$144.60	$144.60
7 purchase totals =	$714.79		$765.0474	$765.06	$765.05	$765.10