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	$144.93	5.275%	$152.5751	$152.58	$152.60	$152.60
Purchase #2	$87.79	3.581%	$90.9338	$90.93	$90.95	$90.90
Purchase #3	$60.58	7.429%	$65.0805	$65.08	$65.10	$65.10
Purchase #4	$51.61	12.568%	$58.0963	$58.10	$58.10	$58.10
Purchase #5	$81.59	4.803%	$85.5088	$85.51	$85.50	$85.50
Purchase #6	$91.94	13.167%	$104.0457	$104.05	$104.05	$104.00
Purchase #7	$226.52	8.384%	$245.5114	$245.51	$245.50	$245.50
7 purchase totals =	$744.96		$801.7516	$801.76	$801.80	$801.70