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	$9.49	5.863%	$10.0464	$10.05	$10.05	$10.00
Purchase #2	$174.45	9.197%	$190.4942	$190.49	$190.50	$190.50
Purchase #3	$96.92	13.375%	$109.8831	$109.88	$109.90	$109.90
Purchase #4	$93.87	8.353%	$101.711	$101.71	$101.70	$101.70
Purchase #5	$9.56	8.267%	$10.3503	$10.35	$10.35	$10.40
Purchase #6	$86.83	3.281%	$89.6789	$89.68	$89.70	$89.70
Purchase #7	$96.31	6.352%	$102.4276	$102.43	$102.45	$102.40
7 purchase totals =	$567.43		$614.5915	$614.59	$614.65	$614.60