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	$141.46	8.463%	$153.4318	$153.43	$153.45	$153.40
Purchase #2	$163.86	5.539%	$172.9362	$172.94	$172.95	$172.90
Purchase #3	$45.38	5.431%	$47.8446	$47.84	$47.85	$47.80
Purchase #4	$61.31	6.870%	$65.522	$65.52	$65.50	$65.50
Purchase #5	$250.25	12.248%	$280.9006	$280.90	$280.90	$280.90
Purchase #6	$86.60	4.121%	$90.1688	$90.17	$90.15	$90.20
Purchase #7	$53.55	12.552%	$60.2716	$60.27	$60.25	$60.30
7 purchase totals =	$802.41		$871.0756	$871.07	$871.05	$871.00