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	$102.25	9.512%	$111.976	$111.98	$112.00	$112.00
Purchase #2	$78.72	4.836%	$82.5269	$82.53	$82.55	$82.50
Purchase #3	$105.96	11.571%	$118.2206	$118.22	$118.20	$118.20
Purchase #4	$126.27	3.388%	$130.548	$130.55	$130.55	$130.50
Purchase #5	$211.39	12.670%	$238.1731	$238.17	$238.15	$238.20
Purchase #6	$102.69	13.337%	$116.3858	$116.39	$116.40	$116.40
Purchase #7	$216.75	12.127%	$243.0353	$243.04	$243.05	$243.00
7 purchase totals =	$944.03		$1,040.8657	$1,040.88	$1,040.90	$1,040.80