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	$48.39	10.638%	$53.5377	$53.54	$53.55	$53.50
Purchase #2	$92.49	11.466%	$103.0949	$103.09	$103.10	$103.10
Purchase #3	$12.27	3.759%	$12.7312	$12.73	$12.75	$12.70
Purchase #4	$165.68	7.574%	$178.2286	$178.23	$178.25	$178.20
Purchase #5	$39.42	12.651%	$44.407	$44.41	$44.40	$44.40
Purchase #6	$156.56	5.590%	$165.3117	$165.31	$165.30	$165.30
Purchase #7	$37.37	5.691%	$39.4967	$39.50	$39.50	$39.50
7 purchase totals =	$552.18		$596.8078	$596.81	$596.85	$596.70