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	$81.91	9.118%	$89.3786	$89.38	$89.40	$89.40
Purchase #2	$110.98	6.685%	$118.399	$118.40	$118.40	$118.40
Purchase #3	$228.75	11.538%	$255.1432	$255.14	$255.15	$255.10
Purchase #4	$208.61	6.155%	$221.4499	$221.45	$221.45	$221.40
Purchase #5	$212.58	3.311%	$219.6185	$219.62	$219.60	$219.60
Purchase #6	$13.52	8.752%	$14.7033	$14.70	$14.70	$14.70
Purchase #7	$137.46	11.772%	$153.6418	$153.64	$153.65	$153.60
7 purchase totals =	$993.81		$1,072.3343	$1,072.33	$1,072.35	$1,072.20