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	$41.25	8.196%	$44.6309	$44.63	$44.65	$44.60
Purchase #2	$64.78	11.452%	$72.1986	$72.20	$72.20	$72.20
Purchase #3	$115.61	12.361%	$129.9006	$129.90	$129.90	$129.90
Purchase #4	$215.83	10.542%	$238.5828	$238.58	$238.60	$238.60
Purchase #5	$25.64	8.307%	$27.7699	$27.77	$27.75	$27.80
Purchase #6	$9.88	9.691%	$10.8375	$10.84	$10.85	$10.80
Purchase #7	$37.56	7.549%	$40.3954	$40.40	$40.40	$40.40
7 purchase totals =	$510.55		$564.3157	$564.32	$564.35	$564.30