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	$203.59	13.258%	$230.582	$230.58	$230.60	$230.60
Purchase #2	$92.30	12.831%	$104.143	$104.14	$104.15	$104.10
Purchase #3	$185.79	3.306%	$191.9322	$191.93	$191.95	$191.90
Purchase #4	$76.99	6.454%	$81.9589	$81.96	$81.95	$82.00
Purchase #5	$164.34	5.606%	$173.5529	$173.55	$173.55	$173.60
Purchase #6	$229.31	6.526%	$244.2748	$244.27	$244.25	$244.30
Purchase #7	$148.32	3.526%	$153.5498	$153.55	$153.55	$153.50
7 purchase totals =	$1,100.64		$1,179.9936	$1,179.98	$1,180.00	$1,180.00