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	$103.25	8.787%	$112.3226	$112.32	$112.30	$112.30
Purchase #2	$73.96	11.785%	$82.6762	$82.68	$82.70	$82.70
Purchase #3	$99.36	12.106%	$111.3885	$111.39	$111.40	$111.40
Purchase #4	$231.58	5.381%	$244.0413	$244.04	$244.05	$244.00
Purchase #5	$164.60	11.685%	$183.8335	$183.83	$183.85	$183.80
Purchase #6	$84.57	5.458%	$89.1858	$89.19	$89.20	$89.20
Purchase #7	$117.95	3.402%	$121.9627	$121.96	$121.95	$122.00
7 purchase totals =	$875.27		$945.4106	$945.41	$945.45	$945.40