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	$79.47	8.260%	$86.0342	$86.03	$86.05	$86.00
Purchase #2	$235.97	8.597%	$256.2563	$256.26	$256.25	$256.30
Purchase #3	$112.50	9.785%	$123.5081	$123.51	$123.50	$123.50
Purchase #4	$156.43	10.732%	$173.2181	$173.22	$173.20	$173.20
Purchase #5	$20.88	13.606%	$23.7209	$23.72	$23.70	$23.70
Purchase #6	$73.93	5.666%	$78.1189	$78.12	$78.10	$78.10
Purchase #7	$131.37	9.403%	$143.7227	$143.72	$143.70	$143.70
7 purchase totals =	$810.55		$884.5792	$884.58	$884.50	$884.50