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	$66.82	8.714%	$72.6427	$72.64	$72.65	$72.60
Purchase #2	$99.56	7.268%	$106.796	$106.80	$106.80	$106.80
Purchase #3	$100.57	3.296%	$103.8848	$103.88	$103.90	$103.90
Purchase #4	$200.33	9.848%	$220.0585	$220.06	$220.05	$220.10
Purchase #5	$141.45	7.161%	$151.5792	$151.58	$151.60	$151.60
Purchase #6	$142.77	5.495%	$150.6152	$150.62	$150.60	$150.60
Purchase #7	$92.58	5.766%	$97.9182	$97.92	$97.90	$97.90
7 purchase totals =	$844.08		$903.4946	$903.50	$903.50	$903.50