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	$172.97	3.632%	$179.2523	$179.25	$179.25	$179.30
Purchase #2	$212.86	5.676%	$224.9419	$224.94	$224.95	$224.90
Purchase #3	$166.73	13.786%	$189.7154	$189.72	$189.70	$189.70
Purchase #4	$242.85	6.823%	$259.4197	$259.42	$259.40	$259.40
Purchase #5	$41.96	7.383%	$45.0579	$45.06	$45.05	$45.10
Purchase #6	$117.42	11.605%	$131.0466	$131.05	$131.05	$131.00
Purchase #7	$43.62	9.104%	$47.5912	$47.59	$47.60	$47.60
7 purchase totals =	$998.41		$1,077.0250	$1,077.03	$1,077.00	$1,077.00