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	$152.60	9.324%	$166.8284	$166.83	$166.85	$166.80
Purchase #2	$192.89	3.583%	$199.8012	$199.80	$199.80	$199.80
Purchase #3	$42.57	4.285%	$44.3941	$44.39	$44.40	$44.40
Purchase #4	$92.89	13.592%	$105.5156	$105.52	$105.50	$105.50
Purchase #5	$112.87	9.418%	$123.5001	$123.50	$123.50	$123.50
Purchase #6	$247.44	9.760%	$271.5901	$271.59	$271.60	$271.60
Purchase #7	$6.74	7.627%	$7.2541	$7.25	$7.25	$7.30
7 purchase totals =	$848.00		$918.8836	$918.88	$918.90	$918.90