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	$193.93	11.448%	$216.1311	$216.13	$216.15	$216.10
Purchase #2	$198.70	6.404%	$211.4247	$211.42	$211.40	$211.40
Purchase #3	$166.72	7.461%	$179.159	$179.16	$179.15	$179.20
Purchase #4	$136.94	4.661%	$143.3228	$143.32	$143.30	$143.30
Purchase #5	$121.42	13.205%	$137.4535	$137.45	$137.45	$137.50
Purchase #6	$102.64	9.386%	$112.2738	$112.27	$112.25	$112.30
Purchase #7	$29.67	6.693%	$31.6558	$31.66	$31.65	$31.70
7 purchase totals =	$950.02		$1,031.4207	$1,031.41	$1,031.35	$1,031.50