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	$138.67	3.705%	$143.8077	$143.81	$143.80	$143.80
Purchase #2	$107.32	11.297%	$119.4439	$119.44	$119.45	$119.40
Purchase #3	$191.53	11.201%	$212.9833	$212.98	$213.00	$213.00
Purchase #4	$238.62	13.337%	$270.4447	$270.44	$270.45	$270.40
Purchase #5	$231.32	4.415%	$241.5328	$241.53	$241.55	$241.50
Purchase #6	$181.94	4.462%	$190.0582	$190.06	$190.05	$190.10
Purchase #7	$108.64	13.650%	$123.4694	$123.47	$123.45	$123.50
7 purchase totals =	$1,198.04		$1,301.7400	$1,301.73	$1,301.75	$1,301.70