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	$179.28	9.613%	$196.5142	$196.51	$196.50	$196.50
Purchase #2	$108.28	13.601%	$123.0072	$123.01	$123.00	$123.00
Purchase #3	$189.62	7.457%	$203.76	$203.76	$203.75	$203.80
Purchase #4	$192.32	13.285%	$217.8697	$217.87	$217.85	$217.90
Purchase #5	$231.48	6.614%	$246.7901	$246.79	$246.80	$246.80
Purchase #6	$133.59	5.452%	$140.8733	$140.87	$140.85	$140.90
Purchase #7	$82.94	10.426%	$91.5873	$91.59	$91.60	$91.60
7 purchase totals =	$1,117.51		$1,220.4018	$1,220.40	$1,220.35	$1,220.50