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	$40.68	8.110%	$43.9791	$43.98	$44.00	$44.00
Purchase #2	$97.84	7.610%	$105.2856	$105.29	$105.30	$105.30
Purchase #3	$204.30	13.488%	$231.856	$231.86	$231.85	$231.90
Purchase #4	$31.25	7.509%	$33.5966	$33.60	$33.60	$33.60
Purchase #5	$184.33	3.271%	$190.3594	$190.36	$190.35	$190.40
Purchase #6	$235.99	13.716%	$268.3584	$268.36	$268.35	$268.40
Purchase #7	$100.52	5.220%	$105.7671	$105.77	$105.75	$105.80
7 purchase totals =	$894.91		$979.2022	$979.22	$979.20	$979.40