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	$179.77	7.192%	$192.6991	$192.70	$192.70	$192.70
Purchase #2	$242.71	11.843%	$271.4541	$271.45	$271.45	$271.50
Purchase #3	$212.54	4.665%	$222.455	$222.46	$222.45	$222.50
Purchase #4	$217.57	4.158%	$226.6166	$226.62	$226.60	$226.60
Purchase #5	$61.89	8.685%	$67.2651	$67.27	$67.25	$67.30
Purchase #6	$17.32	9.350%	$18.9394	$18.94	$18.95	$18.90
Purchase #7	$131.45	3.747%	$136.3754	$136.38	$136.40	$136.40
7 purchase totals =	$1,063.25		$1,135.8047	$1,135.82	$1,135.80	$1,135.90