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	$240.41	9.422%	$263.0614	$263.06	$263.05	$263.10
Purchase #2	$178.45	3.862%	$185.3417	$185.34	$185.35	$185.30
Purchase #3	$84.77	6.630%	$90.3903	$90.39	$90.40	$90.40
Purchase #4	$170.82	4.504%	$178.5137	$178.51	$178.50	$178.50
Purchase #5	$153.86	10.752%	$170.403	$170.40	$170.40	$170.40
Purchase #6	$193.81	5.783%	$205.018	$205.02	$205.00	$205.00
Purchase #7	$34.34	12.786%	$38.7307	$38.73	$38.75	$38.70
7 purchase totals =	$1,056.46		$1,131.4588	$1,131.45	$1,131.45	$1,131.40