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	$164.94	6.119%	$175.0327	$175.03	$175.05	$175.00
Purchase #2	$143.34	12.107%	$160.6942	$160.69	$160.70	$160.70
Purchase #3	$188.81	12.222%	$211.8864	$211.89	$211.90	$211.90
Purchase #4	$13.64	13.358%	$15.462	$15.46	$15.45	$15.50
Purchase #5	$34.45	11.412%	$38.3814	$38.38	$38.40	$38.40
Purchase #6	$71.35	9.670%	$78.2495	$78.25	$78.25	$78.20
Purchase #7	$15.94	3.845%	$16.5529	$16.55	$16.55	$16.60
7 purchase totals =	$632.47		$696.2591	$696.25	$696.30	$696.30