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	$180.39	9.843%	$198.1458	$198.15	$198.15	$198.10
Purchase #2	$100.61	3.704%	$104.3366	$104.34	$104.35	$104.30
Purchase #3	$92.45	12.768%	$104.254	$104.25	$104.25	$104.30
Purchase #4	$26.52	5.841%	$28.069	$28.07	$28.05	$28.10
Purchase #5	$109.86	11.299%	$122.2731	$122.27	$122.25	$122.30
Purchase #6	$42.60	11.485%	$47.4926	$47.49	$47.50	$47.50
Purchase #7	$186.59	7.268%	$200.1514	$200.15	$200.15	$200.20
7 purchase totals =	$739.02		$804.7225	$804.72	$804.70	$804.80