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	$222.50	10.687%	$246.2786	$246.28	$246.30	$246.30
Purchase #2	$220.87	3.193%	$227.9224	$227.92	$227.90	$227.90
Purchase #3	$13.61	12.841%	$15.3577	$15.36	$15.35	$15.40
Purchase #4	$232.26	10.196%	$255.9412	$255.94	$255.95	$255.90
Purchase #5	$176.75	10.138%	$194.6689	$194.67	$194.65	$194.70
Purchase #6	$100.54	10.737%	$111.335	$111.34	$111.35	$111.30
Purchase #7	$82.92	7.609%	$89.2294	$89.23	$89.25	$89.20
7 purchase totals =	$1,049.45		$1,140.7332	$1,140.74	$1,140.75	$1,140.70