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	$98.38	13.790%	$111.9466	$111.95	$111.95	$111.90
Purchase #2	$42.37	5.392%	$44.6546	$44.65	$44.65	$44.70
Purchase #3	$57.50	3.633%	$59.589	$59.59	$59.60	$59.60
Purchase #4	$145.65	12.818%	$164.3194	$164.32	$164.30	$164.30
Purchase #5	$27.35	9.584%	$29.9712	$29.97	$29.95	$30.00
Purchase #6	$56.93	12.245%	$63.9011	$63.90	$63.90	$63.90
Purchase #7	$129.25	11.170%	$143.6872	$143.69	$143.70	$143.70
7 purchase totals =	$557.43		$618.0691	$618.07	$618.05	$618.10