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	$101.43	11.463%	$113.0569	$113.06	$113.05	$113.10
Purchase #2	$97.51	8.293%	$105.5965	$105.60	$105.60	$105.60
Purchase #3	$48.63	9.191%	$53.0996	$53.10	$53.10	$53.10
Purchase #4	$51.96	11.354%	$57.8595	$57.86	$57.85	$57.90
Purchase #5	$150.99	6.709%	$161.1199	$161.12	$161.10	$161.10
Purchase #6	$151.93	4.469%	$158.7198	$158.72	$158.70	$158.70
Purchase #7	$154.83	11.133%	$172.0672	$172.07	$172.05	$172.10
7 purchase totals =	$757.28		$821.5194	$821.53	$821.45	$821.60