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	$115.80	11.491%	$129.1066	$129.11	$129.10	$129.10
Purchase #2	$127.77	11.724%	$142.7498	$142.75	$142.75	$142.70
Purchase #3	$77.61	10.552%	$85.7994	$85.80	$85.80	$85.80
Purchase #4	$166.95	5.678%	$176.4294	$176.43	$176.45	$176.40
Purchase #5	$200.44	11.467%	$223.4245	$223.42	$223.40	$223.40
Purchase #6	$168.42	10.404%	$185.9424	$185.94	$185.95	$185.90
Purchase #7	$199.34	13.131%	$225.5153	$225.52	$225.50	$225.50
7 purchase totals =	$1,056.33		$1,168.9674	$1,168.97	$1,168.95	$1,168.80