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	$112.35	3.707%	$116.5148	$116.51	$116.50	$116.50
Purchase #2	$183.28	4.682%	$191.8612	$191.86	$191.85	$191.90
Purchase #3	$78.94	3.786%	$81.9287	$81.93	$81.95	$81.90
Purchase #4	$156.26	11.275%	$173.8783	$173.88	$173.90	$173.90
Purchase #5	$156.75	11.152%	$174.2308	$174.23	$174.25	$174.20
Purchase #6	$150.32	9.250%	$164.2246	$164.22	$164.20	$164.20
Purchase #7	$83.57	4.124%	$87.0164	$87.02	$87.00	$87.00
7 purchase totals =	$921.47		$989.6548	$989.65	$989.65	$989.60