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	$48.30	12.373%	$54.2762	$54.28	$54.30	$54.30
Purchase #2	$94.84	12.482%	$106.6779	$106.68	$106.70	$106.70
Purchase #3	$88.72	13.376%	$100.5872	$100.59	$100.60	$100.60
Purchase #4	$123.26	11.321%	$137.2143	$137.21	$137.20	$137.20
Purchase #5	$141.31	10.605%	$156.2959	$156.30	$156.30	$156.30
Purchase #6	$177.98	10.500%	$196.6679	$196.67	$196.65	$196.70
Purchase #7	$137.49	5.107%	$144.5116	$144.51	$144.50	$144.50
7 purchase totals =	$811.90		$896.2310	$896.24	$896.25	$896.30