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	$155.47	4.606%	$162.6309	$162.63	$162.65	$162.60
Purchase #2	$129.98	7.191%	$139.3269	$139.33	$139.35	$139.30
Purchase #3	$14.44	3.247%	$14.9089	$14.91	$14.90	$14.90
Purchase #4	$54.71	8.629%	$59.4309	$59.43	$59.45	$59.40
Purchase #5	$249.29	8.652%	$270.8586	$270.86	$270.85	$270.90
Purchase #6	$73.40	9.603%	$80.4486	$80.45	$80.45	$80.40
Purchase #7	$203.98	10.751%	$225.9099	$225.91	$225.90	$225.90
7 purchase totals =	$881.27		$953.5147	$953.52	$953.55	$953.40