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	$230.46	10.103%	$253.7434	$253.74	$253.75	$253.70
Purchase #2	$39.27	10.826%	$43.5214	$43.52	$43.50	$43.50
Purchase #3	$219.67	7.533%	$236.2177	$236.22	$236.20	$236.20
Purchase #4	$80.95	12.142%	$90.7789	$90.78	$90.80	$90.80
Purchase #5	$32.43	5.167%	$34.1057	$34.11	$34.10	$34.10
Purchase #6	$221.50	6.722%	$236.3892	$236.39	$236.40	$236.40
Purchase #7	$164.96	4.468%	$172.3304	$172.33	$172.35	$172.30
7 purchase totals =	$989.24		$1,067.0867	$1,067.09	$1,067.10	$1,067.00