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	$212.30	7.152%	$227.4837	$227.48	$227.50	$227.50
Purchase #2	$228.47	5.690%	$241.4699	$241.47	$241.45	$241.50
Purchase #3	$89.93	6.680%	$95.9373	$95.94	$95.95	$95.90
Purchase #4	$213.49	9.490%	$233.7502	$233.75	$233.75	$233.80
Purchase #5	$134.60	7.662%	$144.9131	$144.91	$144.90	$144.90
Purchase #6	$132.89	6.872%	$142.0222	$142.02	$142.00	$142.00
Purchase #7	$246.33	10.655%	$272.5765	$272.58	$272.60	$272.60
7 purchase totals =	$1,258.01		$1,358.1529	$1,358.15	$1,358.15	$1,358.20