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	$112.58	9.659%	$123.4541	$123.45	$123.45	$123.50
Purchase #2	$124.78	13.864%	$142.0795	$142.08	$142.10	$142.10
Purchase #3	$137.87	11.494%	$153.7168	$153.72	$153.70	$153.70
Purchase #4	$75.82	3.653%	$78.5897	$78.59	$78.60	$78.60
Purchase #5	$195.61	4.749%	$204.8995	$204.90	$204.90	$204.90
Purchase #6	$234.99	12.110%	$263.4473	$263.45	$263.45	$263.40
Purchase #7	$5.71	7.294%	$6.1265	$6.13	$6.15	$6.10
7 purchase totals =	$887.36		$972.3134	$972.32	$972.35	$972.30