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	$57.91	3.784%	$60.1013	$60.10	$60.10	$60.10
Purchase #2	$172.56	3.525%	$178.6427	$178.64	$178.65	$178.60
Purchase #3	$66.89	7.533%	$71.9288	$71.93	$71.95	$71.90
Purchase #4	$22.82	6.828%	$24.3781	$24.38	$24.40	$24.40
Purchase #5	$130.85	13.538%	$148.5645	$148.56	$148.55	$148.60
Purchase #6	$63.27	4.563%	$66.157	$66.16	$66.15	$66.20
Purchase #7	$152.69	9.725%	$167.5391	$167.54	$167.55	$167.50
7 purchase totals =	$666.99		$717.3115	$717.31	$717.35	$717.30