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	$223.89	11.504%	$249.6463	$249.65	$249.65	$249.60
Purchase #2	$132.50	9.135%	$144.6039	$144.60	$144.60	$144.60
Purchase #3	$97.69	12.842%	$110.2353	$110.24	$110.25	$110.20
Purchase #4	$157.40	9.403%	$172.2003	$172.20	$172.20	$172.20
Purchase #5	$95.89	9.264%	$104.7732	$104.77	$104.75	$104.80
Purchase #6	$131.76	12.581%	$148.3367	$148.34	$148.35	$148.30
Purchase #7	$151.80	8.382%	$164.5239	$164.52	$164.50	$164.50
7 purchase totals =	$990.93		$1,094.3196	$1,094.32	$1,094.30	$1,094.20