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	$58.62	8.616%	$63.6707	$63.67	$63.65	$63.70
Purchase #2	$83.88	9.821%	$92.1179	$92.12	$92.10	$92.10
Purchase #3	$58.35	12.626%	$65.7173	$65.72	$65.70	$65.70
Purchase #4	$24.40	12.764%	$27.5144	$27.51	$27.50	$27.50
Purchase #5	$86.42	4.829%	$90.5932	$90.59	$90.60	$90.60
Purchase #6	$213.32	5.521%	$225.0974	$225.10	$225.10	$225.10
Purchase #7	$25.51	7.574%	$27.4421	$27.44	$27.45	$27.40
7 purchase totals =	$550.50		$592.1530	$592.15	$592.10	$592.10