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	$200.44	4.718%	$209.8968	$209.90	$209.90	$209.90
Purchase #2	$229.89	11.150%	$255.5227	$255.52	$255.50	$255.50
Purchase #3	$85.49	8.258%	$92.5498	$92.55	$92.55	$92.50
Purchase #4	$239.31	9.737%	$262.6116	$262.61	$262.60	$262.60
Purchase #5	$114.48	10.518%	$126.521	$126.52	$126.50	$126.50
Purchase #6	$233.49	10.597%	$258.2329	$258.23	$258.25	$258.20
Purchase #7	$211.37	5.179%	$222.3169	$222.32	$222.30	$222.30
7 purchase totals =	$1,314.47		$1,427.6517	$1,427.65	$1,427.60	$1,427.50