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	$98.94	5.758%	$104.637	$104.64	$104.65	$104.60
Purchase #2	$225.29	9.406%	$246.4808	$246.48	$246.50	$246.50
Purchase #3	$241.86	4.653%	$253.1137	$253.11	$253.10	$253.10
Purchase #4	$145.87	4.400%	$152.2883	$152.29	$152.30	$152.30
Purchase #5	$120.59	5.407%	$127.1103	$127.11	$127.10	$127.10
Purchase #6	$218.39	4.789%	$228.8487	$228.85	$228.85	$228.80
Purchase #7	$132.32	7.420%	$142.1381	$142.14	$142.15	$142.10
7 purchase totals =	$1,183.26		$1,254.6169	$1,254.62	$1,254.65	$1,254.50