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	$90.29	11.715%	$100.8675	$100.87	$100.85	$100.90
Purchase #2	$158.25	8.807%	$172.1871	$172.19	$172.20	$172.20
Purchase #3	$93.51	10.332%	$103.1715	$103.17	$103.15	$103.20
Purchase #4	$244.95	4.277%	$255.4265	$255.43	$255.45	$255.40
Purchase #5	$39.70	11.758%	$44.3679	$44.37	$44.35	$44.40
Purchase #6	$12.91	11.229%	$14.3597	$14.36	$14.35	$14.40
Purchase #7	$175.50	5.639%	$185.3964	$185.40	$185.40	$185.40
7 purchase totals =	$815.11		$875.7766	$875.79	$875.75	$875.90