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	$106.60	5.645%	$112.6176	$112.62	$112.60	$112.60
Purchase #2	$241.66	11.338%	$269.0594	$269.06	$269.05	$269.10
Purchase #3	$42.71	6.569%	$45.5156	$45.52	$45.50	$45.50
Purchase #4	$109.47	7.436%	$117.6102	$117.61	$117.60	$117.60
Purchase #5	$33.37	4.386%	$34.8336	$34.83	$34.85	$34.80
Purchase #6	$27.57	7.301%	$29.5829	$29.58	$29.60	$29.60
Purchase #7	$245.51	5.162%	$258.1832	$258.18	$258.20	$258.20
7 purchase totals =	$806.89		$867.4025	$867.40	$867.40	$867.40