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	$114.25	10.691%	$126.4645	$126.46	$126.45	$126.50
Purchase #2	$50.48	5.783%	$53.3993	$53.40	$53.40	$53.40
Purchase #3	$42.32	13.504%	$48.0349	$48.03	$48.05	$48.00
Purchase #4	$32.80	5.343%	$34.5525	$34.55	$34.55	$34.60
Purchase #5	$13.94	11.311%	$15.5168	$15.52	$15.50	$15.50
Purchase #6	$164.48	4.414%	$171.7401	$171.74	$171.75	$171.70
Purchase #7	$75.56	10.588%	$83.5603	$83.56	$83.55	$83.60
7 purchase totals =	$493.83		$533.2684	$533.26	$533.25	$533.30