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	$148.81	6.764%	$158.8755	$158.88	$158.90	$158.90
Purchase #2	$176.65	7.276%	$189.5031	$189.50	$189.50	$189.50
Purchase #3	$38.92	3.830%	$40.4106	$40.41	$40.40	$40.40
Purchase #4	$110.76	11.733%	$123.7555	$123.76	$123.75	$123.80
Purchase #5	$22.64	10.138%	$24.9352	$24.94	$24.95	$24.90
Purchase #6	$239.52	7.440%	$257.3403	$257.34	$257.35	$257.30
Purchase #7	$105.37	13.152%	$119.2283	$119.23	$119.25	$119.20
7 purchase totals =	$842.67		$914.0485	$914.06	$914.10	$914.00