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	$99.92	11.735%	$111.6456	$111.65	$111.65	$111.60
Purchase #2	$135.41	7.408%	$145.4412	$145.44	$145.45	$145.40
Purchase #3	$211.25	9.417%	$231.1434	$231.14	$231.15	$231.10
Purchase #4	$123.64	10.172%	$136.2167	$136.22	$136.20	$136.20
Purchase #5	$118.42	7.156%	$126.8941	$126.89	$126.90	$126.90
Purchase #6	$90.91	12.783%	$102.531	$102.53	$102.55	$102.50
Purchase #7	$237.26	10.549%	$262.2886	$262.29	$262.30	$262.30
7 purchase totals =	$1,016.81		$1,116.1606	$1,116.16	$1,116.20	$1,116.00