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	$134.32	10.699%	$148.6909	$148.69	$148.70	$148.70
Purchase #2	$217.46	3.830%	$225.7887	$225.79	$225.80	$225.80
Purchase #3	$170.45	3.593%	$176.5743	$176.57	$176.55	$176.60
Purchase #4	$160.69	8.495%	$174.3406	$174.34	$174.35	$174.30
Purchase #5	$245.73	6.742%	$262.2971	$262.30	$262.30	$262.30
Purchase #6	$39.25	4.203%	$40.8997	$40.90	$40.90	$40.90
Purchase #7	$225.96	13.263%	$255.9291	$255.93	$255.95	$255.90
7 purchase totals =	$1,193.86		$1,284.5204	$1,284.52	$1,284.55	$1,284.50