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	$235.73	5.554%	$248.8224	$248.82	$248.80	$248.80
Purchase #2	$117.58	7.306%	$126.1704	$126.17	$126.15	$126.20
Purchase #3	$205.71	12.575%	$231.578	$231.58	$231.60	$231.60
Purchase #4	$227.98	12.682%	$256.8924	$256.89	$256.90	$256.90
Purchase #5	$50.38	6.416%	$53.6124	$53.61	$53.60	$53.60
Purchase #6	$92.48	13.109%	$104.6032	$104.60	$104.60	$104.60
Purchase #7	$124.72	9.486%	$136.5509	$136.55	$136.55	$136.60
7 purchase totals =	$1,054.58		$1,158.2297	$1,158.22	$1,158.20	$1,158.30