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	$105.75	6.761%	$112.8998	$112.90	$112.90	$112.90
Purchase #2	$222.78	8.192%	$241.0301	$241.03	$241.05	$241.00
Purchase #3	$208.69	8.549%	$226.5309	$226.53	$226.55	$226.50
Purchase #4	$92.56	8.526%	$100.4517	$100.45	$100.45	$100.50
Purchase #5	$210.48	4.233%	$219.3896	$219.39	$219.40	$219.40
Purchase #6	$17.82	7.406%	$19.1397	$19.14	$19.15	$19.10
Purchase #7	$174.88	6.595%	$186.4133	$186.41	$186.40	$186.40
7 purchase totals =	$1,032.96		$1,105.8551	$1,105.85	$1,105.90	$1,105.80