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	$245.92	12.260%	$276.0698	$276.07	$276.05	$276.10
Purchase #2	$147.45	4.848%	$154.5984	$154.60	$154.60	$154.60
Purchase #3	$142.65	7.459%	$153.2903	$153.29	$153.30	$153.30
Purchase #4	$19.66	9.822%	$21.591	$21.59	$21.60	$21.60
Purchase #5	$211.80	12.518%	$238.3131	$238.31	$238.30	$238.30
Purchase #6	$137.60	10.778%	$152.4305	$152.43	$152.45	$152.40
Purchase #7	$82.38	7.726%	$88.7447	$88.74	$88.75	$88.70
7 purchase totals =	$987.46		$1,085.0378	$1,085.03	$1,085.05	$1,085.00