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	$105.65	11.647%	$117.9551	$117.96	$117.95	$118.00
Purchase #2	$169.53	12.339%	$190.4483	$190.45	$190.45	$190.40
Purchase #3	$91.85	8.707%	$99.8474	$99.85	$99.85	$99.80
Purchase #4	$10.50	11.700%	$11.7285	$11.73	$11.75	$11.70
Purchase #5	$132.84	6.286%	$141.1903	$141.19	$141.20	$141.20
Purchase #6	$139.45	9.377%	$152.5262	$152.53	$152.55	$152.50
Purchase #7	$19.41	12.774%	$21.8894	$21.89	$21.90	$21.90
7 purchase totals =	$669.23		$735.5852	$735.60	$735.65	$735.50