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	$56.67	3.637%	$58.7311	$58.73	$58.75	$58.70
Purchase #2	$182.59	4.109%	$190.0926	$190.09	$190.10	$190.10
Purchase #3	$250.39	9.737%	$274.7705	$274.77	$274.75	$274.80
Purchase #4	$143.54	11.630%	$160.2337	$160.23	$160.25	$160.20
Purchase #5	$231.94	12.464%	$260.849	$260.85	$260.85	$260.80
Purchase #6	$59.69	11.301%	$66.4356	$66.44	$66.45	$66.40
Purchase #7	$170.98	8.544%	$185.5885	$185.59	$185.60	$185.60
7 purchase totals =	$1,095.80		$1,196.7010	$1,196.70	$1,196.75	$1,196.60