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	$142.67	10.329%	$157.4064	$157.41	$157.40	$157.40
Purchase #2	$241.40	13.692%	$274.4525	$274.45	$274.45	$274.50
Purchase #3	$100.32	8.212%	$108.5583	$108.56	$108.55	$108.60
Purchase #4	$64.62	13.339%	$73.2397	$73.24	$73.25	$73.20
Purchase #5	$119.75	12.612%	$134.8529	$134.85	$134.85	$134.90
Purchase #6	$106.89	7.508%	$114.9153	$114.92	$114.90	$114.90
Purchase #7	$128.75	12.141%	$144.3815	$144.38	$144.40	$144.40
7 purchase totals =	$904.40		$1,007.8066	$1,007.81	$1,007.80	$1,007.90