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	$105.51	10.219%	$116.2921	$116.29	$116.30	$116.30
Purchase #2	$82.56	9.231%	$90.1811	$90.18	$90.20	$90.20
Purchase #3	$87.78	5.770%	$92.8449	$92.84	$92.85	$92.80
Purchase #4	$242.55	6.208%	$257.6075	$257.61	$257.60	$257.60
Purchase #5	$238.89	3.792%	$247.9487	$247.95	$247.95	$247.90
Purchase #6	$149.31	10.114%	$164.4112	$164.41	$164.40	$164.40
Purchase #7	$136.47	10.205%	$150.3968	$150.40	$150.40	$150.40
7 purchase totals =	$1,043.07		$1,119.6823	$1,119.68	$1,119.70	$1,119.60