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	$116.58	9.381%	$127.5164	$127.52	$127.50	$127.50
Purchase #2	$132.43	11.786%	$148.0382	$148.04	$148.05	$148.00
Purchase #3	$212.50	13.165%	$240.4756	$240.48	$240.50	$240.50
Purchase #4	$20.91	3.486%	$21.6389	$21.64	$21.65	$21.60
Purchase #5	$173.91	3.469%	$179.9429	$179.94	$179.95	$179.90
Purchase #6	$138.59	9.645%	$151.957	$151.96	$151.95	$152.00
Purchase #7	$214.60	10.122%	$236.3218	$236.32	$236.30	$236.30
7 purchase totals =	$1,009.52		$1,105.8908	$1,105.90	$1,105.90	$1,105.80