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	$232.50	4.312%	$242.5254	$242.53	$242.55	$242.50
Purchase #2	$34.42	7.201%	$36.8986	$36.90	$36.90	$36.90
Purchase #3	$173.55	5.614%	$183.2931	$183.29	$183.30	$183.30
Purchase #4	$38.56	3.196%	$39.7924	$39.79	$39.80	$39.80
Purchase #5	$100.38	11.492%	$111.9157	$111.92	$111.90	$111.90
Purchase #6	$246.34	4.533%	$257.5066	$257.51	$257.50	$257.50
Purchase #7	$76.63	5.124%	$80.5565	$80.56	$80.55	$80.60
7 purchase totals =	$902.38		$952.4883	$952.50	$952.50	$952.50