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	$36.64	10.585%	$40.5183	$40.52	$40.50	$40.50
Purchase #2	$126.98	5.705%	$134.2242	$134.22	$134.20	$134.20
Purchase #3	$203.63	6.143%	$216.139	$216.14	$216.15	$216.10
Purchase #4	$222.33	3.399%	$229.887	$229.89	$229.90	$229.90
Purchase #5	$227.90	4.836%	$238.9212	$238.92	$238.90	$238.90
Purchase #6	$164.25	6.747%	$175.3319	$175.33	$175.35	$175.30
Purchase #7	$128.75	3.592%	$133.3747	$133.37	$133.35	$133.40
7 purchase totals =	$1,110.48		$1,168.3963	$1,168.39	$1,168.35	$1,168.30