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	$85.75	11.603%	$95.6996	$95.70	$95.70	$95.70
Purchase #2	$53.90	8.333%	$58.3915	$58.39	$58.40	$58.40
Purchase #3	$75.56	13.706%	$85.9163	$85.92	$85.90	$85.90
Purchase #4	$68.49	3.487%	$70.8782	$70.88	$70.90	$70.90
Purchase #5	$192.55	8.368%	$208.6626	$208.66	$208.65	$208.70
Purchase #6	$195.39	5.372%	$205.8864	$205.89	$205.90	$205.90
Purchase #7	$227.38	12.397%	$255.5683	$255.57	$255.55	$255.60
7 purchase totals =	$899.02		$981.0029	$981.01	$981.00	$981.10