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	$219.37	3.402%	$226.833	$226.83	$226.85	$226.80
Purchase #2	$91.65	12.218%	$102.8478	$102.85	$102.85	$102.80
Purchase #3	$242.33	8.480%	$262.8796	$262.88	$262.90	$262.90
Purchase #4	$175.94	5.812%	$186.1656	$186.17	$186.15	$186.20
Purchase #5	$55.83	3.166%	$57.5976	$57.60	$57.60	$57.60
Purchase #6	$32.25	8.185%	$34.8897	$34.89	$34.90	$34.90
Purchase #7	$125.45	13.469%	$142.3469	$142.35	$142.35	$142.30
7 purchase totals =	$942.82		$1,013.5602	$1,013.57	$1,013.60	$1,013.50