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	$216.71	5.859%	$229.407	$229.41	$229.40	$229.40
Purchase #2	$68.28	13.455%	$77.4671	$77.47	$77.45	$77.50
Purchase #3	$12.78	12.382%	$14.3624	$14.36	$14.35	$14.40
Purchase #4	$214.88	6.414%	$228.6624	$228.66	$228.65	$228.70
Purchase #5	$76.82	7.862%	$82.8596	$82.86	$82.85	$82.90
Purchase #6	$214.31	3.600%	$222.0252	$222.03	$222.05	$222.00
Purchase #7	$61.51	7.831%	$66.3268	$66.33	$66.35	$66.30
7 purchase totals =	$865.29		$921.1105	$921.12	$921.10	$921.20