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	$217.92	4.411%	$227.5325	$227.53	$227.55	$227.50
Purchase #2	$63.96	12.636%	$72.042	$72.04	$72.05	$72.00
Purchase #3	$27.95	12.221%	$31.3658	$31.37	$31.35	$31.40
Purchase #4	$105.68	13.576%	$120.0271	$120.03	$120.05	$120.00
Purchase #5	$116.41	8.639%	$126.4667	$126.47	$126.45	$126.50
Purchase #6	$102.52	9.164%	$111.9149	$111.91	$111.90	$111.90
Purchase #7	$9.46	7.428%	$10.1627	$10.16	$10.15	$10.20
7 purchase totals =	$643.90		$699.5117	$699.51	$699.50	$699.50