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	$109.26	9.709%	$119.8681	$119.87	$119.85	$119.90
Purchase #2	$196.37	5.312%	$206.8012	$206.80	$206.80	$206.80
Purchase #3	$87.78	9.867%	$96.4413	$96.44	$96.45	$96.40
Purchase #4	$167.88	8.502%	$182.1532	$182.15	$182.15	$182.20
Purchase #5	$226.49	12.650%	$255.141	$255.14	$255.15	$255.10
Purchase #6	$126.86	13.666%	$144.1967	$144.20	$144.20	$144.20
Purchase #7	$102.27	9.279%	$111.7596	$111.76	$111.75	$111.80
7 purchase totals =	$1,016.91		$1,116.3611	$1,116.36	$1,116.35	$1,116.40