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	$174.92	11.155%	$194.4323	$194.43	$194.45	$194.40
Purchase #2	$47.57	8.523%	$51.6244	$51.62	$51.60	$51.60
Purchase #3	$133.34	7.360%	$143.1538	$143.15	$143.15	$143.20
Purchase #4	$118.78	7.560%	$127.7598	$127.76	$127.75	$127.80
Purchase #5	$51.31	10.856%	$56.8802	$56.88	$56.90	$56.90
Purchase #6	$58.35	4.405%	$60.9203	$60.92	$60.90	$60.90
Purchase #7	$36.82	13.228%	$41.6905	$41.69	$41.70	$41.70
7 purchase totals =	$621.09		$676.4613	$676.45	$676.45	$676.50