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	$183.97	6.783%	$196.4487	$196.45	$196.45	$196.40
Purchase #2	$246.33	3.520%	$255.0008	$255.00	$255.00	$255.00
Purchase #3	$88.46	13.351%	$100.2703	$100.27	$100.25	$100.30
Purchase #4	$139.71	9.679%	$153.2325	$153.23	$153.25	$153.20
Purchase #5	$50.57	12.199%	$56.739	$56.74	$56.75	$56.70
Purchase #6	$82.41	4.431%	$86.0616	$86.06	$86.05	$86.10
Purchase #7	$18.95	6.381%	$20.1592	$20.16	$20.15	$20.20
7 purchase totals =	$810.40		$867.9121	$867.91	$867.90	$867.90