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	$62.57	9.106%	$68.2676	$68.27	$68.25	$68.30
Purchase #2	$150.38	11.507%	$167.6842	$167.68	$167.70	$167.70
Purchase #3	$18.77	13.351%	$21.276	$21.28	$21.30	$21.30
Purchase #4	$211.88	12.614%	$238.6065	$238.61	$238.60	$238.60
Purchase #5	$81.92	10.851%	$90.8091	$90.81	$90.80	$90.80
Purchase #6	$155.58	8.498%	$168.8012	$168.80	$168.80	$168.80
Purchase #7	$126.90	13.534%	$144.0746	$144.07	$144.05	$144.10
7 purchase totals =	$808.00		$899.5192	$899.52	$899.50	$899.60