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	$49.40	4.503%	$51.6245	$51.62	$51.60	$51.60
Purchase #2	$57.81	5.689%	$61.0988	$61.10	$61.10	$61.10
Purchase #3	$166.32	6.154%	$176.5553	$176.56	$176.55	$176.60
Purchase #4	$38.47	9.606%	$42.1654	$42.17	$42.15	$42.20
Purchase #5	$63.54	5.677%	$67.1472	$67.15	$67.15	$67.10
Purchase #6	$247.51	13.150%	$280.0576	$280.06	$280.05	$280.10
Purchase #7	$80.35	10.699%	$88.9466	$88.95	$88.95	$88.90
7 purchase totals =	$703.40		$767.5954	$767.61	$767.55	$767.60