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	$161.64	12.422%	$181.7189	$181.72	$181.70	$181.70
Purchase #2	$228.91	11.654%	$255.5872	$255.59	$255.60	$255.60
Purchase #3	$29.71	12.662%	$33.4719	$33.47	$33.45	$33.50
Purchase #4	$73.54	5.617%	$77.6707	$77.67	$77.65	$77.70
Purchase #5	$36.77	7.595%	$39.5627	$39.56	$39.55	$39.60
Purchase #6	$120.76	11.457%	$134.5955	$134.60	$134.60	$134.60
Purchase #7	$133.96	9.324%	$146.4504	$146.45	$146.45	$146.50
7 purchase totals =	$785.29		$869.0573	$869.06	$869.00	$869.20