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	$165.56	3.495%	$171.3463	$171.35	$171.35	$171.30
Purchase #2	$15.83	4.802%	$16.5902	$16.59	$16.60	$16.60
Purchase #3	$166.82	5.665%	$176.2704	$176.27	$176.25	$176.30
Purchase #4	$57.45	3.787%	$59.6256	$59.63	$59.65	$59.60
Purchase #5	$77.86	10.379%	$85.9411	$85.94	$85.95	$85.90
Purchase #6	$246.97	5.243%	$259.9186	$259.92	$259.90	$259.90
Purchase #7	$148.32	9.395%	$162.2547	$162.25	$162.25	$162.30
7 purchase totals =	$878.81		$931.9469	$931.95	$931.95	$931.90