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	$212.55	4.392%	$221.8852	$221.89	$221.90	$221.90
Purchase #2	$221.53	3.571%	$229.4408	$229.44	$229.45	$229.40
Purchase #3	$19.69	11.265%	$21.9081	$21.91	$21.90	$21.90
Purchase #4	$111.77	11.787%	$124.9443	$124.94	$124.95	$124.90
Purchase #5	$119.43	9.230%	$130.4534	$130.45	$130.45	$130.50
Purchase #6	$111.52	10.335%	$123.0456	$123.05	$123.05	$123.00
Purchase #7	$129.67	10.752%	$143.6121	$143.61	$143.60	$143.60
7 purchase totals =	$926.16		$995.2895	$995.29	$995.30	$995.20