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	$46.32	13.208%	$52.4379	$52.44	$52.45	$52.40
Purchase #2	$122.30	6.415%	$130.1455	$130.15	$130.15	$130.10
Purchase #3	$73.92	10.303%	$81.536	$81.54	$81.55	$81.50
Purchase #4	$86.92	13.470%	$98.6281	$98.63	$98.65	$98.60
Purchase #5	$99.66	11.650%	$111.2704	$111.27	$111.25	$111.30
Purchase #6	$76.71	10.227%	$84.5551	$84.56	$84.55	$84.60
Purchase #7	$54.40	8.765%	$59.1682	$59.17	$59.15	$59.20
7 purchase totals =	$560.23		$617.7412	$617.76	$617.75	$617.70