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	$79.79	9.301%	$87.2113	$87.21	$87.20	$87.20
Purchase #2	$99.81	9.630%	$109.4217	$109.42	$109.40	$109.40
Purchase #3	$208.61	5.706%	$220.5133	$220.51	$220.50	$220.50
Purchase #4	$105.25	12.677%	$118.5925	$118.59	$118.60	$118.60
Purchase #5	$149.64	10.574%	$165.4629	$165.46	$165.45	$165.50
Purchase #6	$136.26	4.603%	$142.532	$142.53	$142.55	$142.50
Purchase #7	$183.52	9.174%	$200.3561	$200.36	$200.35	$200.40
7 purchase totals =	$962.88		$1,044.0898	$1,044.08	$1,044.05	$1,044.10