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	$99.67	4.261%	$103.9169	$103.92	$103.90	$103.90
Purchase #2	$52.56	5.209%	$55.2979	$55.30	$55.30	$55.30
Purchase #3	$67.45	4.641%	$70.5804	$70.58	$70.60	$70.60
Purchase #4	$202.35	12.157%	$226.9497	$226.95	$226.95	$226.90
Purchase #5	$121.29	4.608%	$126.879	$126.88	$126.90	$126.90
Purchase #6	$150.86	7.191%	$161.7083	$161.71	$161.70	$161.70
Purchase #7	$35.54	13.310%	$40.2704	$40.27	$40.25	$40.30
7 purchase totals =	$729.72		$785.6026	$785.61	$785.60	$785.60