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	$122.34	4.746%	$128.1463	$128.15	$128.15	$128.10
Purchase #2	$137.87	4.625%	$144.2465	$144.25	$144.25	$144.20
Purchase #3	$160.57	7.522%	$172.6481	$172.65	$172.65	$172.60
Purchase #4	$214.41	3.681%	$222.3024	$222.30	$222.30	$222.30
Purchase #5	$138.47	9.274%	$151.3117	$151.31	$151.30	$151.30
Purchase #6	$185.97	4.291%	$193.95	$193.95	$193.95	$194.00
Purchase #7	$93.31	12.678%	$105.1398	$105.14	$105.15	$105.10
7 purchase totals =	$1,052.94		$1,117.7448	$1,117.75	$1,117.75	$1,117.60