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	$186.84	8.274%	$202.2991	$202.30	$202.30	$202.30
Purchase #2	$149.65	5.328%	$157.6234	$157.62	$157.60	$157.60
Purchase #3	$100.55	10.817%	$111.4265	$111.43	$111.45	$111.40
Purchase #4	$81.38	11.621%	$90.8372	$90.84	$90.85	$90.80
Purchase #5	$57.46	10.752%	$63.6381	$63.64	$63.65	$63.60
Purchase #6	$152.79	5.258%	$160.8237	$160.82	$160.80	$160.80
Purchase #7	$207.73	12.242%	$233.1603	$233.16	$233.15	$233.20
7 purchase totals =	$936.40		$1,019.8083	$1,019.81	$1,019.80	$1,019.70