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	$172.41	13.769%	$196.1491	$196.15	$196.15	$196.10
Purchase #2	$105.98	10.577%	$117.1895	$117.19	$117.20	$117.20
Purchase #3	$12.29	3.569%	$12.7286	$12.73	$12.75	$12.70
Purchase #4	$100.49	11.685%	$112.2323	$112.23	$112.25	$112.20
Purchase #5	$33.70	10.795%	$37.3379	$37.34	$37.35	$37.30
Purchase #6	$234.75	12.221%	$263.4388	$263.44	$263.45	$263.40
Purchase #7	$202.88	11.445%	$226.0996	$226.10	$226.10	$226.10
7 purchase totals =	$862.50		$965.1758	$965.18	$965.25	$965.00