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	$43.71	6.486%	$46.545	$46.55	$46.55	$46.50
Purchase #2	$19.66	4.161%	$20.4781	$20.48	$20.50	$20.50
Purchase #3	$19.54	6.755%	$20.8599	$20.86	$20.85	$20.90
Purchase #4	$170.43	13.111%	$192.7751	$192.78	$192.80	$192.80
Purchase #5	$86.54	3.195%	$89.305	$89.31	$89.30	$89.30
Purchase #6	$55.49	10.149%	$61.1217	$61.12	$61.10	$61.10
Purchase #7	$70.34	8.153%	$76.0748	$76.07	$76.05	$76.10
7 purchase totals =	$465.71		$507.1596	$507.17	$507.15	$507.20