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	$68.73	10.621%	$76.0298	$76.03	$76.05	$76.00
Purchase #2	$143.61	4.737%	$150.4128	$150.41	$150.40	$150.40
Purchase #3	$131.77	12.564%	$148.3256	$148.33	$148.35	$148.30
Purchase #4	$110.44	7.693%	$118.9361	$118.94	$118.95	$118.90
Purchase #5	$105.88	5.266%	$111.4556	$111.46	$111.45	$111.50
Purchase #6	$195.86	3.434%	$202.5858	$202.59	$202.60	$202.60
Purchase #7	$233.68	9.306%	$255.4263	$255.43	$255.45	$255.40
7 purchase totals =	$989.97		$1,063.1720	$1,063.19	$1,063.25	$1,063.10