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	$160.61	11.496%	$179.0737	$179.07	$179.05	$179.10
Purchase #2	$38.97	11.593%	$43.4878	$43.49	$43.50	$43.50
Purchase #3	$19.74	8.519%	$21.4217	$21.42	$21.40	$21.40
Purchase #4	$131.31	8.329%	$142.2468	$142.25	$142.25	$142.20
Purchase #5	$48.45	12.625%	$54.5668	$54.57	$54.55	$54.60
Purchase #6	$125.86	8.717%	$136.8312	$136.83	$136.85	$136.80
Purchase #7	$103.27	9.378%	$112.9547	$112.95	$112.95	$113.00
7 purchase totals =	$628.21		$690.5827	$690.58	$690.55	$690.60