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	$151.50	8.533%	$164.4275	$164.43	$164.45	$164.40
Purchase #2	$198.58	5.561%	$209.623	$209.62	$209.60	$209.60
Purchase #3	$199.59	6.653%	$212.8687	$212.87	$212.85	$212.90
Purchase #4	$128.65	12.616%	$144.8805	$144.88	$144.90	$144.90
Purchase #5	$117.82	4.572%	$123.2067	$123.21	$123.20	$123.20
Purchase #6	$238.93	12.341%	$268.4164	$268.42	$268.40	$268.40
Purchase #7	$224.92	6.223%	$238.9168	$238.92	$238.90	$238.90
7 purchase totals =	$1,259.99		$1,362.3396	$1,362.35	$1,362.30	$1,362.30