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	$208.34	12.835%	$235.0804	$235.08	$235.10	$235.10
Purchase #2	$42.83	8.372%	$46.4157	$46.42	$46.40	$46.40
Purchase #3	$139.37	9.194%	$152.1837	$152.18	$152.20	$152.20
Purchase #4	$19.53	8.299%	$21.1508	$21.15	$21.15	$21.20
Purchase #5	$234.72	9.429%	$256.8517	$256.85	$256.85	$256.90
Purchase #6	$136.89	10.416%	$151.1485	$151.15	$151.15	$151.10
Purchase #7	$193.66	11.613%	$216.1497	$216.15	$216.15	$216.10
7 purchase totals =	$975.34		$1,078.9805	$1,078.98	$1,079.00	$1,079.00