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	$107.32	10.525%	$118.6154	$118.62	$118.60	$118.60
Purchase #2	$45.39	13.603%	$51.5644	$51.56	$51.55	$51.60
Purchase #3	$162.40	3.533%	$168.1376	$168.14	$168.15	$168.10
Purchase #4	$145.45	9.149%	$158.7572	$158.76	$158.75	$158.80
Purchase #5	$140.54	9.513%	$153.9096	$153.91	$153.90	$153.90
Purchase #6	$58.35	3.598%	$60.4494	$60.45	$60.45	$60.40
Purchase #7	$64.54	13.830%	$73.4659	$73.47	$73.45	$73.50
7 purchase totals =	$723.99		$784.8995	$784.91	$784.85	$784.90