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	$187.90	4.396%	$196.1601	$196.16	$196.15	$196.20
Purchase #2	$100.97	10.493%	$111.5648	$111.56	$111.55	$111.60
Purchase #3	$162.52	6.269%	$172.7084	$172.71	$172.70	$172.70
Purchase #4	$55.29	5.810%	$58.5023	$58.50	$58.50	$58.50
Purchase #5	$242.90	5.167%	$255.4506	$255.45	$255.45	$255.50
Purchase #6	$181.98	6.333%	$193.5048	$193.50	$193.50	$193.50
Purchase #7	$215.93	3.349%	$223.1615	$223.16	$223.15	$223.20
7 purchase totals =	$1,147.49		$1,211.0525	$1,211.04	$1,211.00	$1,211.20