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	$52.48	11.235%	$58.3761	$58.38	$58.40	$58.40
Purchase #2	$239.27	7.466%	$257.1339	$257.13	$257.15	$257.10
Purchase #3	$129.30	13.634%	$146.9288	$146.93	$146.95	$146.90
Purchase #4	$63.89	9.748%	$70.118	$70.12	$70.10	$70.10
Purchase #5	$228.31	13.504%	$259.141	$259.14	$259.15	$259.10
Purchase #6	$160.77	13.595%	$182.6267	$182.63	$182.65	$182.60
Purchase #7	$42.88	5.116%	$45.0737	$45.07	$45.05	$45.10
7 purchase totals =	$916.90		$1,019.3982	$1,019.40	$1,019.45	$1,019.30