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	$56.98	8.186%	$61.6444	$61.64	$61.65	$61.60
Purchase #2	$214.88	9.558%	$235.4182	$235.42	$235.40	$235.40
Purchase #3	$96.59	7.145%	$103.4914	$103.49	$103.50	$103.50
Purchase #4	$58.50	5.172%	$61.5256	$61.53	$61.55	$61.50
Purchase #5	$204.56	9.317%	$223.6189	$223.62	$223.60	$223.60
Purchase #6	$87.79	5.346%	$92.4833	$92.48	$92.50	$92.50
Purchase #7	$121.31	5.242%	$127.6691	$127.67	$127.65	$127.70
7 purchase totals =	$840.61		$905.8509	$905.85	$905.85	$905.80