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	$183.45	5.809%	$194.1066	$194.11	$194.10	$194.10
Purchase #2	$103.82	7.524%	$111.6314	$111.63	$111.65	$111.60
Purchase #3	$176.78	3.547%	$183.0504	$183.05	$183.05	$183.10
Purchase #4	$76.66	11.606%	$85.5572	$85.56	$85.55	$85.60
Purchase #5	$41.64	4.657%	$43.5792	$43.58	$43.60	$43.60
Purchase #6	$157.95	7.776%	$170.2322	$170.23	$170.25	$170.20
Purchase #7	$218.94	4.252%	$228.2493	$228.25	$228.25	$228.20
7 purchase totals =	$959.24		$1,016.4063	$1,016.41	$1,016.45	$1,016.40