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	$65.42	9.636%	$71.7239	$71.72	$71.70	$71.70
Purchase #2	$74.77	5.524%	$78.9003	$78.90	$78.90	$78.90
Purchase #3	$10.97	5.625%	$11.5871	$11.59	$11.60	$11.60
Purchase #4	$133.28	3.239%	$137.5969	$137.60	$137.60	$137.60
Purchase #5	$48.26	12.787%	$54.431	$54.43	$54.45	$54.40
Purchase #6	$94.60	12.129%	$106.074	$106.07	$106.05	$106.10
Purchase #7	$163.54	3.613%	$169.4487	$169.45	$169.45	$169.40
7 purchase totals =	$590.84		$629.7619	$629.76	$629.75	$629.70