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	$122.38	3.221%	$126.3219	$126.32	$126.30	$126.30
Purchase #2	$225.35	13.377%	$255.4951	$255.50	$255.50	$255.50
Purchase #3	$190.78	6.685%	$203.5336	$203.53	$203.55	$203.50
Purchase #4	$217.86	3.869%	$226.289	$226.29	$226.30	$226.30
Purchase #5	$245.62	12.202%	$275.5906	$275.59	$275.60	$275.60
Purchase #6	$24.44	5.718%	$25.8375	$25.84	$25.85	$25.80
Purchase #7	$117.82	11.631%	$131.5236	$131.52	$131.50	$131.50
7 purchase totals =	$1,144.25		$1,244.5913	$1,244.59	$1,244.60	$1,244.50