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	$82.70	9.480%	$90.54	$90.54	$90.55	$90.50
Purchase #2	$164.42	11.479%	$183.2938	$183.29	$183.30	$183.30
Purchase #3	$122.77	7.756%	$132.292	$132.29	$132.30	$132.30
Purchase #4	$240.94	10.387%	$265.9664	$265.97	$265.95	$266.00
Purchase #5	$84.26	13.761%	$95.855	$95.86	$95.85	$95.90
Purchase #6	$226.64	11.795%	$253.3722	$253.37	$253.35	$253.40
Purchase #7	$94.70	11.712%	$105.7913	$105.79	$105.80	$105.80
7 purchase totals =	$1,016.43		$1,127.1107	$1,127.11	$1,127.10	$1,127.20