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	$214.32	7.247%	$229.8518	$229.85	$229.85	$229.90
Purchase #2	$115.62	9.103%	$126.1449	$126.14	$126.15	$126.10
Purchase #3	$114.96	13.459%	$130.4325	$130.43	$130.45	$130.40
Purchase #4	$52.93	3.178%	$54.6121	$54.61	$54.60	$54.60
Purchase #5	$86.95	3.616%	$90.0941	$90.09	$90.10	$90.10
Purchase #6	$152.75	12.705%	$172.1569	$172.16	$172.15	$172.20
Purchase #7	$188.63	7.796%	$203.3356	$203.34	$203.35	$203.30
7 purchase totals =	$926.16		$1,006.6279	$1,006.62	$1,006.65	$1,006.60