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	$97.67	13.208%	$110.5703	$110.57	$110.55	$110.60
Purchase #2	$109.63	12.268%	$123.0794	$123.08	$123.10	$123.10
Purchase #3	$246.56	4.152%	$256.7972	$256.80	$256.80	$256.80
Purchase #4	$164.29	12.300%	$184.4977	$184.50	$184.50	$184.50
Purchase #5	$65.75	11.313%	$73.1883	$73.19	$73.20	$73.20
Purchase #6	$10.75	10.650%	$11.8949	$11.89	$11.90	$11.90
Purchase #7	$225.85	10.600%	$249.7901	$249.79	$249.80	$249.80
7 purchase totals =	$920.50		$1,009.8179	$1,009.82	$1,009.85	$1,009.90