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	$112.70	12.211%	$126.4618	$126.46	$126.45	$126.50
Purchase #2	$183.37	4.535%	$191.6858	$191.69	$191.70	$191.70
Purchase #3	$127.67	12.305%	$143.3798	$143.38	$143.40	$143.40
Purchase #4	$87.59	10.449%	$96.7423	$96.74	$96.75	$96.70
Purchase #5	$173.87	9.817%	$190.9388	$190.94	$190.95	$190.90
Purchase #6	$227.54	10.518%	$251.4727	$251.47	$251.45	$251.50
Purchase #7	$213.53	4.468%	$223.0705	$223.07	$223.05	$223.10
7 purchase totals =	$1,126.27		$1,223.7517	$1,223.75	$1,223.75	$1,223.80