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	$176.40	13.796%	$200.7361	$200.74	$200.75	$200.70
Purchase #2	$88.75	13.791%	$100.9895	$100.99	$101.00	$101.00
Purchase #3	$100.92	11.694%	$112.7216	$112.72	$112.70	$112.70
Purchase #4	$15.73	6.310%	$16.7226	$16.72	$16.70	$16.70
Purchase #5	$87.43	3.180%	$90.2103	$90.21	$90.20	$90.20
Purchase #6	$119.84	9.808%	$131.5939	$131.59	$131.60	$131.60
Purchase #7	$240.36	9.380%	$262.9058	$262.91	$262.90	$262.90
7 purchase totals =	$829.43		$915.8798	$915.88	$915.85	$915.80