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	$138.32	3.834%	$143.6232	$143.62	$143.60	$143.60
Purchase #2	$50.32	5.259%	$52.9663	$52.97	$52.95	$53.00
Purchase #3	$100.59	10.696%	$111.3491	$111.35	$111.35	$111.30
Purchase #4	$157.89	3.161%	$162.8809	$162.88	$162.90	$162.90
Purchase #5	$171.49	3.791%	$177.9912	$177.99	$178.00	$178.00
Purchase #6	$174.91	13.137%	$197.8879	$197.89	$197.90	$197.90
Purchase #7	$10.31	10.627%	$11.4056	$11.41	$11.40	$11.40
7 purchase totals =	$803.83		$858.1042	$858.11	$858.10	$858.10