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	$214.99	6.320%	$228.5774	$228.58	$228.60	$228.60
Purchase #2	$79.89	12.349%	$89.7556	$89.76	$89.75	$89.80
Purchase #3	$179.56	13.763%	$204.2728	$204.27	$204.25	$204.30
Purchase #4	$74.78	9.763%	$82.0808	$82.08	$82.10	$82.10
Purchase #5	$213.67	4.487%	$223.2574	$223.26	$223.25	$223.30
Purchase #6	$104.58	8.102%	$113.0531	$113.05	$113.05	$113.10
Purchase #7	$219.45	3.483%	$227.0934	$227.09	$227.10	$227.10
7 purchase totals =	$1,086.92		$1,168.0905	$1,168.09	$1,168.10	$1,168.30