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	$53.93	7.239%	$57.834	$57.83	$57.85	$57.80
Purchase #2	$73.52	6.725%	$78.4642	$78.46	$78.45	$78.50
Purchase #3	$135.25	9.573%	$148.1975	$148.20	$148.20	$148.20
Purchase #4	$50.37	5.378%	$53.0789	$53.08	$53.10	$53.10
Purchase #5	$94.56	6.202%	$100.4246	$100.42	$100.40	$100.40
Purchase #6	$58.88	7.647%	$63.3826	$63.38	$63.40	$63.40
Purchase #7	$190.77	11.796%	$213.2732	$213.27	$213.25	$213.30
7 purchase totals =	$657.28		$714.6550	$714.64	$714.65	$714.70