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	$177.86	10.633%	$196.7719	$196.77	$196.75	$196.80
Purchase #2	$153.31	4.659%	$160.4527	$160.45	$160.45	$160.50
Purchase #3	$198.87	7.420%	$213.6262	$213.63	$213.65	$213.60
Purchase #4	$205.34	5.191%	$215.9992	$216.00	$216.00	$216.00
Purchase #5	$167.88	3.814%	$174.2829	$174.28	$174.30	$174.30
Purchase #6	$11.72	6.716%	$12.5071	$12.51	$12.50	$12.50
Purchase #7	$36.63	6.303%	$38.9388	$38.94	$38.95	$38.90
7 purchase totals =	$951.61		$1,012.5788	$1,012.58	$1,012.60	$1,012.60