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	$144.31	8.639%	$156.7769	$156.78	$156.80	$156.80
Purchase #2	$176.45	7.545%	$189.7632	$189.76	$189.75	$189.80
Purchase #3	$159.34	8.443%	$172.7931	$172.79	$172.80	$172.80
Purchase #4	$53.81	10.727%	$59.5822	$59.58	$59.60	$59.60
Purchase #5	$8.83	11.708%	$9.8638	$9.86	$9.85	$9.90
Purchase #6	$214.65	4.454%	$224.2105	$224.21	$224.20	$224.20
Purchase #7	$109.90	9.689%	$120.5482	$120.55	$120.55	$120.50
7 purchase totals =	$867.29		$933.5379	$933.53	$933.55	$933.60