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	$185.69	12.622%	$209.1278	$209.13	$209.15	$209.10
Purchase #2	$44.72	10.818%	$49.5578	$49.56	$49.55	$49.60
Purchase #3	$5.43	3.680%	$5.6298	$5.63	$5.65	$5.60
Purchase #4	$48.56	4.104%	$50.5529	$50.55	$50.55	$50.60
Purchase #5	$98.91	12.835%	$111.6051	$111.61	$111.60	$111.60
Purchase #6	$174.71	13.431%	$198.1753	$198.18	$198.20	$198.20
Purchase #7	$81.37	10.178%	$89.6518	$89.65	$89.65	$89.70
7 purchase totals =	$639.39		$714.3005	$714.31	$714.35	$714.40