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	$145.79	8.416%	$158.0597	$158.06	$158.05	$158.10
Purchase #2	$69.84	4.686%	$73.1127	$73.11	$73.10	$73.10
Purchase #3	$225.37	13.265%	$255.2653	$255.27	$255.25	$255.30
Purchase #4	$171.64	6.123%	$182.1495	$182.15	$182.15	$182.10
Purchase #5	$144.96	13.690%	$164.805	$164.81	$164.80	$164.80
Purchase #6	$59.69	8.230%	$64.6025	$64.60	$64.60	$64.60
Purchase #7	$118.84	10.631%	$131.4739	$131.47	$131.45	$131.50
7 purchase totals =	$936.13		$1,029.4686	$1,029.47	$1,029.40	$1,029.50