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	$42.73	6.803%	$45.6369	$45.64	$45.65	$45.60
Purchase #2	$98.92	12.724%	$111.5066	$111.51	$111.50	$111.50
Purchase #3	$156.38	13.665%	$177.7493	$177.75	$177.75	$177.70
Purchase #4	$218.39	7.613%	$235.016	$235.02	$235.00	$235.00
Purchase #5	$187.37	3.672%	$194.2502	$194.25	$194.25	$194.30
Purchase #6	$88.51	10.852%	$98.1151	$98.12	$98.10	$98.10
Purchase #7	$230.92	13.150%	$261.286	$261.29	$261.30	$261.30
7 purchase totals =	$1,023.22		$1,123.5601	$1,123.58	$1,123.55	$1,123.50