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	$116.96	13.556%	$132.8151	$132.82	$132.80	$132.80
Purchase #2	$103.33	7.433%	$111.0105	$111.01	$111.00	$111.00
Purchase #3	$102.46	6.511%	$109.1312	$109.13	$109.15	$109.10
Purchase #4	$27.89	3.640%	$28.9052	$28.91	$28.90	$28.90
Purchase #5	$217.35	4.204%	$226.4874	$226.49	$226.50	$226.50
Purchase #6	$249.74	6.695%	$266.4601	$266.46	$266.45	$266.50
Purchase #7	$122.97	6.792%	$131.3221	$131.32	$131.30	$131.30
7 purchase totals =	$940.70		$1,006.1316	$1,006.14	$1,006.10	$1,006.10