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	$182.71	11.254%	$203.2722	$203.27	$203.25	$203.30
Purchase #2	$49.27	7.140%	$52.7879	$52.79	$52.80	$52.80
Purchase #3	$85.93	5.358%	$90.5341	$90.53	$90.55	$90.50
Purchase #4	$94.83	5.611%	$100.1509	$100.15	$100.15	$100.20
Purchase #5	$134.76	11.200%	$149.8531	$149.85	$149.85	$149.90
Purchase #6	$218.81	11.758%	$244.5377	$244.54	$244.55	$244.50
Purchase #7	$30.52	6.699%	$32.5645	$32.56	$32.55	$32.60
7 purchase totals =	$796.83		$873.7004	$873.69	$873.70	$873.80