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	$134.64	7.403%	$144.6074	$144.61	$144.60	$144.60
Purchase #2	$116.86	10.197%	$128.7762	$128.78	$128.80	$128.80
Purchase #3	$107.27	5.207%	$112.8555	$112.86	$112.85	$112.90
Purchase #4	$110.38	8.127%	$119.3506	$119.35	$119.35	$119.40
Purchase #5	$129.72	11.766%	$144.9829	$144.98	$145.00	$145.00
Purchase #6	$71.79	9.648%	$78.7163	$78.72	$78.70	$78.70
Purchase #7	$62.29	8.784%	$67.7616	$67.76	$67.75	$67.80
7 purchase totals =	$732.95		$797.0505	$797.06	$797.05	$797.20