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	$44.58	8.161%	$48.2182	$48.22	$48.20	$48.20
Purchase #2	$21.45	11.350%	$23.8846	$23.88	$23.90	$23.90
Purchase #3	$92.36	10.811%	$102.345	$102.35	$102.35	$102.30
Purchase #4	$212.57	13.301%	$240.8439	$240.84	$240.85	$240.80
Purchase #5	$97.31	8.245%	$105.3332	$105.33	$105.35	$105.30
Purchase #6	$238.40	10.858%	$264.2855	$264.29	$264.30	$264.30
Purchase #7	$226.89	12.609%	$255.4986	$255.50	$255.50	$255.50
7 purchase totals =	$933.56		$1,040.4090	$1,040.41	$1,040.45	$1,040.30