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	$14.59	4.608%	$15.2623	$15.26	$15.25	$15.30
Purchase #2	$95.97	13.153%	$108.5929	$108.59	$108.60	$108.60
Purchase #3	$187.52	10.644%	$207.4796	$207.48	$207.50	$207.50
Purchase #4	$93.37	11.205%	$103.8321	$103.83	$103.85	$103.80
Purchase #5	$150.77	3.425%	$155.9339	$155.93	$155.95	$155.90
Purchase #6	$12.77	8.823%	$13.8967	$13.90	$13.90	$13.90
Purchase #7	$57.33	9.436%	$62.7397	$62.74	$62.75	$62.70
7 purchase totals =	$612.32		$667.7372	$667.73	$667.80	$667.70